A suspension sub frame structure comprises a suspension sub frame provided to extend in a vehicle longitudinal direction and supporting a suspension link, an extension frame provided to extend forwardly from a front end of the suspension sub frame and having lower rigidity against a load applied in the vehicle longitudinal direction than the suspension sub frame, and a cross member provided to extend in a vehicle width direction on an inward side, in the vehicle width direction, of the both frames, wherein the cross member is joined to the both frames at a joint area which is continuous in the vehicle longitudinal direction.