The problem to be solved by the present invention is to provide an anticancer agent for treating tumors resistant to other antitumor agents that inhibit FGFR, and a method for treating such tumors. The present invention provides an antitumor agent for administration to a tumor patient resistant to an FGFR inhibitor, the antitumor agent comprising a 3,5-disubstituted benzene alkynyl compound represented by Formula (I) below or a salt thereof. The present invention also provides a therapeutic method using the anticancer agent.
