An instrument panel is provided with an upper panel of a synthetic resin disposed on the front side, and a core panel of a synthetic resin retentive of shape and connected to the rear side of the upper panel. The core panel has a casing portion which has an opening portion opened in an air bag-protruding direction and which receives a folded air bag of a passenger seat air bag unit and an inflator for supplying an inflating gas to the air bag. The upper panel has door portions which cover the casing portion and which are pressed and opened by the air bag when the air bag is inflated.