The present invention provides a bicyclic γ-amino-acid derivative that have excellent activity as α2δ ligand.The present invention relates to a compound of the following formula(I)[wherein, R1, R2, R2’, R4, R5, R6, R7, R8and R8represents a hydrogen atoms etc., and R3represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group etc.].提供作為α2δ配體具有優異活性之二環性γ-胺基酸衍生物。如下如下式(I)化合物:[式中R1、R2、R2’、R4、R5、R6、R7、R8及R8’為氫原子等,R3為氫原子、鹵原子、C1-C6烷基等]。