To provide a resin panel capable of being formed easily and inexpensively without using a slidable mold and an under cover for an automobile, in integrally forming an opening and a cover for closing the opening on the bottom plane of projection of a bridge-form projected part disposed on the front face side of the resin panel.

An under cover 10 is provided with a bridge-form installing seat 12 projected like a bridge and formed as an integrated body (together with the cover 10) so that the cover 10 can be attached to a front bumper by means of a resin clip. The bottom plane of projection of the bridge-form installing seat 12 is provided with an opening 14 larger than the width of the bridge-form installing seat 12 in the direction normal to the bridge forming direction and on the bottom plane of projection of the seat 12, along the direction normal to the bridge forming direction. In the opening 14, a thin wall hinge mechanism 15a for opening/closing the opening 14 and a cover 15 having claws 16, 16 for fixing the cover after the opening is closed are formed as an integrated body.