The present invention provides a quinazoline derivative represented by the following formula (I): wherein R 1 and R 2 represent a hydrogen atom, a halogen atom, or a lower alkyl group optionally having a substituent Z represents a cycloalkyl group having a substituent or a cycloalkenyl group having a substituent and Q represents a bicyclic heteroaryl group optionally having a substituent, or a pharmaceutically acceptable salt thereof. Since the compound has an inhibitory effect on the Wnt/²-catenin signaling pathway and exhibits an antitumor effect, it is useful as a medicine.
