A joining mechanism includes a front lower cross member 110 formed from a front plate 112 and a back plate 114 joined together to form a space, the front lower cross member 110 extending in a vehicle width direction lower than a hood lock member 108 which supports a bottom part of the vicinity of a front end of an engine hood 104, and a hood lock brace 120 which extends in a vehicle height direction between the hood lock member 108 and the front lower cross member 110, the hood lock brace 120 joining the hood lock member 108 and the front lower cross member 110, wherein upper end vicinities of the front plate 112 and the back plate 114 of the front lower cross member 110 are fastened to the front side of the hood lock brace 120, and the upper end surface 112j of the front plate 112 and the upper end surface 114j of the back plate 114 are separated from the hood lock brace 120.