Abstract: The subject of this research is Immanuel Kant’s concept of free will. The article presents critical analysis of this concept and demonstrates its ambiguity. Special attention is given to Kant’s teaching on the transcendental and practical freedom, as well as the concept of the autonomy of will. If during precritical period, Kant adhered to the traditional compatibilism, then during critical period, the philosopher created compatibilistic concept of the new type. Its distinction from his previous views is defined by the idea of independence of the free will from external circumstances. Research methodology synthesizes the historical-philosophical reconstruction of the Kant’s concept of free will with the critical conceptual analysis of its main principles. The article demonstrates the invalidity of opinions of the researchers who attempted to show that Kant advocated incompatibilism. The difficulties faced by Kant’s concept of free will relate to ambiguity of his perceptions on the thing in itself, autonomy of will, as well as improper substantiation of the thesis and antithesis of the third antinomy. The incorrectness of Kant’s teaching on the autonomy of will has a range of aspects: 1) impossibility to release the idea of universal legislation from the idea of the autonomy of will; 2) inaccuracy of the teaching on categorical imperative; 3) groundlessness of the opinion that only moral acts are free; 4) cognitivism; 5) ambiguity of Kant’s perception on the definition of will.