It is shown that steady and laminar shock waves can propagate along a uniform magnetic field in a hot collisionless plasma. These shock waves are exact numerical solutions of the Vlasov-Maxwell equations except for the assumption that distribution functions of ions and electrons have nonzero values only at some discrete points in the velocity space. No irreversible mechanism, such as anomalous resistivity, is introduced to derive the shock-type solutions. It is found that the longitudinal collisionless shock waves are not so effective for the heating of plasma as expected from the classical gasdynamic shock relations.