It is intended to provide a bicyclic .gamma.-amino acidderivative having excellent activity as an .alpha.2.delta. ligand. Thepresent invention provides a compound represented by thegeneral formula (I):(see formula I)wherein R1, R2, R2 R4, R5, R6, R7, R8, and R8' are a hydrogenatom or the like; and R3 is a hydrogen atom, a halogen atom,a C1-C6 alkyl group, or the like.