A compound having antiviral activity, specifically a heterocyclic compound having HIV integrase inhibitory activity; and a medicine containing the compound, especially an anti-HIV drug. The compound is a compound represented by the formula (I): (I) [wherein B1 is -C(R2)= or -N=; R1' is hydrogen, etc.; one of R1 and R2 is a group represented by the formula -Z1-Z2-Z3-R5 (wherein Z1 and Z3 each independently is a single bond, optionally substituted alkylene, etc.; Z2 is a single bond, optionally substituted alkylene, etc.; and R5 is optionally substituted aryl, optionally substituted heteroaryl, etc.) and the other is hydrogen; and -A1- is -C(-Y)=C(-RA)-C(-R3)=C(-R4)- (wherein Y is -OH, etc.; RA is -COR7 (R7 is hydroxy, etc.), etc.; and one of R3 and R4 is carboxy, etc. and the other is hydrogen, etc.), etc.], a prodrug of the compound, a pharmaceutically acceptable salt of either, or a solvate of any of these.