  We study gamma ray and positron in high energy cosmic ray from the decay of
the gravitino dark matter in the framework of supersymmetric model with
R-parity violation. Even though R-parity is violated, the lifetime of the
gravitino, which is assumed to be the lightest superparticle, can be longer
than the present age of the universe if R-parity violating interactions are
weak enough. In such a case, gravitino can be dark matter of the universe and
its decay produces high energy cosmic rays. We calculate the fluxes of gamma
ray and positron from the decay of the gravitino dark matter and discuss
implications of such a scenario to present and future observations. In
particular, we show that excesses of the fluxes of gamma ray and positron
observed by EGRET and HEAT experiments, respectively, can be simultaneously
explained as the cosmic rays from the decay of the gravitino dark matter.
