The present invention addresses the problem of providing an antitumor agent that is exceptional as a treatment agent for the prevention and/or treatment of tumors involving bromodomains, and providing a bromodomain inhibitor that is useful as a treatment agent for diseases or conditions involving bromodomains. An antitumor agent and bromodomain inhibitor containing a compound represented by the general formula [in the formula, R1 represents a C1-6 alkyl group, etc.； R2 represents a hydrogen atom, etc.； R3 represents a halogen atom, etc.； Z1, Z2, and Z3 represent CH, etc.； X1 represents CONH, etc.； ring A represents a phenyl group, etc.； R4 represents a halogen atom, etc.； and m represents an integer of 0-5] have exceptional bromodomain inhibitory activity and are useful as treatment agents for the prevention and/or treatment of tumors involving bromodomains.
