However Frege was a mathematicians he is regarded as a philosopher who pointed out the paradigm of philosophical analysis in the XXth century. Frege’s method of philosophical analysis could be describe as rational investigation of objective, invariable and eternal objects like numbers, thought and truth. There are following “tools” used in his philosophical analysis: distinction between function and its argument, semantics and logic. In spite of the fact that Frege did not present conception of his analysis it is possible to reconstruct it on the ground of his writings. In the first chapter named Introducing Problems I present Frege’s philosophy on the background of German philosophy in the XIXth century. Next I consider how to describe analytical philosophy and if Frege’s philosophy could be treated as an example of the approach. Then I introduce an analysis as a method of philosophy. In the second chapter Types of Analysis I describe three types of analysis used by Frege. The basic one is analysis using mathematical distinction between function (described as a constant element which needs to be completed by argument) and its argument (described as a interchangable element which does not need to be completed). In this example analysis is a process of breaking down judgeable content into two elements: one playing a part of function and the other of its argument. The next is a language analysis which is grounded on his investigation of natural language and its semantics in which Frege made use of the context principle and the sense-reference distinction). His logical analysis relies on using the conceptual notation (named Begriffsschrift). I describe his semantics conceptual notation and present the historical development of it in Frege’s writings. It could be said that logical analysis begins there where there are assertion, proposition, truth-values and the correct structure of the sentence. Logical analysis is a process of breaking the sentence down into its logical components to show logical structure of the sentence if need be to correct the logical structure of the sentence. Analysis is not the only methodological operation used by Frege, there are also defining, elucidation and reasoning by analogy too. In order to underline Frege’s understanding and the aim of analysis I describe these methodological operations. In the third chapter Analysing and other Cognitional Actions I present Frege’s conception of definition and elucidation. Both are distinguish from analysis. Analysing, defining and elucidating deal with three different notions: 1) analysable, that means capable of being divided into parts; 2) definable meaning possible to describe clearly by using logical notions, 3) primitive terms (named also as logical simple) which are not analysable and not definable only elucidated. In this chapter I show some examples of reasoning by analogy from Frege’s writings. In the last chapter Investigation of Philosophical Problems I try to show how Frege’s method is used to investigate philosophical subjects like: What is a number? What is truth? He distinguished number as German’s Zahl which is undefined, untemporal and unspatial but a real object and number as Anzahl which can be defined and gives us answer to the question: how many things are there? The last one is the famous Frege’s definition of number by abstraction which turned out as paradigm of philosophical analysis in XXth century. Therefore, it is interesting to list his steps how to deal with philosophical problems: 1) According to context principle, the central word from your philosophical problem put into a natural language sentence. 2) Break the sentence down to show its part saturated (interchangeable) and the one unsaturated (constant) 3) Determine to which part of sentence your word belongs. 4) If all words in the sentence have reference, the sentence has its reference too, it is true or false. If there are words in the sentence without references the sentence has no truth-values. Nonetheless it could have its sense. 5) (If need be) Consider which words of the sentence could be replaced so that: a) the truth-value of the sentence is the same (salva veritate); b) the new sentence is still judgeable content (salva congruitate) 6) Remember that scientific sentence which has no truth-values express no thought; 7) Using conceptual notation (named as Begriffsschrift) present correct logical structure of the sentence and next make it concrete according the given sentence; 8) If the investigate a word is simply one: a) Do its definition if it is definable; remember about conditions of correct definition; b) Do its elucidation if it is simple and undefinable; 9) To do complex investigation use Frege’s ontological determinations, like distinction between object and concept or three realms (spatio-temporal objects, subjective experiences and unspatio and untemporal objects like truth, numbers and thoughts). However it was the Frege’s way of doing philosophy, his investigation of truth was not by using the above scheme because of nature of truth. There is no one conception of truth in Frege’s philosophy. He began with truth in the background of judgement and finished with truth understood as one of two truth-values which is a real (but not temporal and not spatial) object that cannot be defined. Finally in Appendix I present some information about Frege’s life and his academic development.