The invention provides an impact absorbing member of a motor vehicle which can correspond to an energy caused by a low impact value (5 kN or lower) as well as absorbing an energy caused by a high impact value (20 kN or higher) at a time of being collided with and brought into contact with the other motor vehicle or the other body, can secure a desired impact absorbing performance even in the case that a thickness of an impact absorbing member is limited, is particularly excellent in an impact absorbing performance just after an impact is applied, and is excellent in a functionality and a styling characteristic which can maintain a high impact absorbing performance.An impact absorbing member (1, 11) of a motor vehicle is interposed between a bumper facia (2, 12) and a vehicle body so as to absorb an impact, and is constituted by a bumper beam (3, 13) arranged in a side of the vehicle body, and a hollow body (4, 14) arranged in a side of the bumper facia (2, 12). The hollow body (4, 14) structuring the impact-absorbing member (1, 11) for the vehicle is formed by blow molding thermoplastic plastics. A plurality of concave ribs constituted by one concave ribs (5, 15) and the other concave ribs (6, 16) having weld surfaces (7, 17) which are depressed to an inner side in an opposing manner and are welded to each other are provided in a first wall (8, 18) in a side of the bumper facia (2, 12) and a second wall (9, 19) in a side of the bumper beam in the hollow body (4, 14). Further, a connection rib (26) rising up in a forward moving direction of the motor vehicle is inter posed between the adjacent concave ribs. The concave ribs are arranged on a virtual straight line, and the connection rib (26) is also formed on the virtual straight line. Further, one plate-like rib (22) and the other plate-like rib (23) are formed in the first wall (8, 18) and the second wall (9, 19) so as to connect a plurality of concave ribs (5, 15). The one plate-like rib (22) and the other plate-like rib (23) are integrally formed by welding leading ends thereof to each other by a weld portion (24).