A bonnet inner panel includes a central protrusion portion protruding upward in a vehicle elevational view and a rear protrusion portion located in back of the central protrusion portion, which are arranged side by side in a vehicle longitudinal direction, a deep-drawn groove is provided between the both protrusion portions to extend in a vehicle width direction, and a hinge reinforcement is provided to extend from a position beside the rear protrusion portion to a position at a rear end of the central protrusion portion, passing through beside the deep-drawn groove. Thereby, the hinge support rigidity of the rear portion of the bonnet having the central protrusion portion can be increased, so that occurrence of any improper deflection or vibration caused to the bonnet by the traveling vibration, the traveling-air pressure or the like can be prevented.