The problems to be solved by the present invention are to provide a novel FGFR inhibitor that is potent and highly selective, and to provide an antitumor agent with which side effects such as an elevated blood phosphorus concentration are alleviated while maintaining the antitumor effect of the FGFR inhibitor. The present invention provides an antitumor agent comprising a 3,5-di-substituted benzene alkynyl compound represented by general formula (I) or salt thereof, which is used by administering the 3,5-di-substituted benzene alkynyl compound or salt thereof according to an administration schedule of two or more times/week at an administration interval of at least one day between doses.
