PURPOSE: To shorten manufacturing process by providing plural long grooves in longitudinal direction on upper surface of a hollow frame integrally molded and thus forming the integral mold out of one material.

CONSTITUTION: A bumper 1 is a hollow frame integrally formed out of thermoplastic resin (e.g. polyurethane), to be mounted horizontally at front and rear of a vehicle. Plural long grooves 2 of saw-teeth in section are formed in the middle of the upper face of the bumper 1 in longitudinal direction. Vertical grooves 3 are then formed perpendicularly to the plural long grooves 2. A cut portion 4 is formed in the middle of the front face of the bumper 1 for attaching a number plate, and also positioning holes 5a, 5b are provided fordisposing direction-indicator lamps. Because plural horizontal grooves 2 and vertical grooves 3 are provided on the upper face of the bumper 1, the bumper hardly slips without a member of other material. The manufacturing process is also shortened, thereby reducing the manufacture cost.