  We study Q-ball dark matter in gauge-mediated supersymmetry breaking, and
seek the possibility of detection in the IceCube experiment. We find that the Q
balls would be the dark matter in the parameter region different from that for
gravitino dark matter. In particular, the Q ball is a good dark matter
candidate for low reheating temperature, which may be suitable for the
Affleck-Dine baryogenesis and/or nonthermal leptogenesis. Dark matter Q balls
are detectable by IceCube-like experiments in the future, which is the peculiar
feature compared to the case of gravitino dark matter.
