A sub frame structure of a vehicle comprising a pair of side members with front ends rigidly connected to a floor frame, a rear cross member holding the vicinity of rear ends of the side members, both-side end portions of which are rigidly connected to a rear side frame, the both-side end portions of the rear cross member being positioned on an outward side, in a vehicle width direction, of the side members, a front cross member interconnecting the side members in the vehicle width direction and being positioned in front of the rear cross member, being spaced apart from the rear cross member, and a pair of upper members respectively connecting an upper portion of the rear cross member and an upper portion of the front cross member in a vehicle longitudinal direction at a position above the side member.