L. Petrażycki’s concept of normative motivation may be viewed in perspective of his general sociology and theory of law as theoretical sciences and legal policy as practical science. Discovering this concept first of all in the aspect of theory of law the author proposes an answer to the question how the existence of ought is possible or what are the grounds of the obligatory power of law. Author makes the conclusion, that emotional experience of the self-sufficing value of the appropriate conduct by the subject is the normative-axiological ground of the obligatory power of law. Author rejects thesis about positivistic character of methodological grounds of L. Petrażycki’s legal theory and indicates the opportunity of its phenomenological interpretation.