[Problem] To provide a GPR40 activating agent having, as an active ingredient, a novel compound having a GPR40 agonist action, a salt of the compound, a solvate of the salt or the compound, or the like, particularly, an insulin secretagogue and a prophylactic and/or therapeutic agent against diabetes, obesity, or other diseases. [Means of solving the problem] A compound of Formula (I): (where n is 0 to 2； p is 0 to 4； j is 0 to 3； k is 0 to 2； a ring A is an aryl group which is optionally substituted with L or a heterocyclic group which is optionally substituted with L； a ring B is a benzene ring, a pyridine ring, or a pyrimidine ring； X is O, S, -NR 7 -； and R 1 to R 7 are specific groups), a salt of the compound, or a solvate of the salt or the compound.
