The present invention provides a T-type calcium channel inhibitor which is a compound represented by formula (1), a pharmaceutically acceptable salt of this compound or a solvate of this compound. The present invention also provides: this T-type calcium channel inhibitor； a pharmaceutical product containing this T-type calcium channel inhibitor； and a therapeutic agent or prophylactic agent for diseases, the effective action of which is a T-type calcium channel inhibitory action. (In formula (1), each of R1 and R2 independently represents H, -OH or -OR11, wherein R11 represents a C1-3 alkyl group； each of R3 and R4 independently represents H, -OH or -OR12, wherein R12 represents a C1-3 alkyl group； and each of R5 and R6 independently represents H, a halogen atom, a C1-10 alkyl group, a C2-6 alkenyl group, a C2-6 alkynyl group, a phenyl group (which may be substituted by a C1-6 alkoxy group or a halogen atom), a -C1-3 alkyl-phenyl group (which may be substituted by a C1-6 alkyloxy group or a halogen atom) or a C10-50 prenyl group.)
