It is intended to provide a novel method for treating a cancer using an FGFR inhibitor that exhibits a remarkably excellent antitumor effect and has fewer side effects. The present invention provides a combination preparation for the treatment of a malignant tumor comprising a compound represented by Formula (I) or a pharmaceutically acceptable salt thereof, and one or more additional compound(s) having an antitumor effect or pharmaceutically acceptable salt(s) thereof, and a pharmaceutical composition comprising both the active ingredients. The present invention also provides an antitumor effect enhancer, an antitumor agent, a kit for malignant tumor treatment, etc. comprising a compound represented by Formula (I) or a pharmaceutically acceptable salt thereof.