provided is a shock absorber for a vehicle , which , when it is crushed , can break and open a part of the wall thereof earlier than the time of the break of an explosion inducing section , to thereby exclude the effect of the air being present inside a hollow portion and exhibit stable shock - absorbing capability and also maintain a satisfactory shock - absorbing capability over a wide range of temperature from a high temperature to a low temperature independently of the temperature of the open air . a shock absorber is a hollow structure integrally molded through blow molding . the shock absorber has at least one explosion inducing section . the explosion inducing section comprises a protruded ridge in a notch form formed on the surface of the wall of the shock absorber . the shock absorber comprises a thermoplastic polymer alloy of a polyolefin type resin and an amorphous resin .