  The gauge-mediated SUSY-breaking (GMSB) model needs entropy production at a
relatively low temperature in the thermal history of the Universe for the
unwanted relics to be diluted. This requires a mechanism for the baryogenesis
after the entropy production, and the Affleck and Dine (AD) mechanism is a
promising candidate for it. The AD baryogenesis in the GMSB model predicts the
existence of the baryonic Q ball, that is the B ball, and this may work as the
dark matter in the Universe. In this article, we discuss the stability of the B
ball in th presence of baryon-number violating interactions. We find that the
evaporation rate increases monotonically with the B-ball charge because the
large field value inside the B ball enhances the effect of the
baryon-number-violating operators. While there are some difficulties to
evaluate the evaporation rate of the B ball, we derive the evaporation time
(lifetime) of the B ball for the mass-to-charge ratio $\omega_0\gsim 100 \MEV$.
The lifetime of the B ball and the distortion of the cosmic ray positron flux
and the cosmic background radiation from the B ball evaporation give
constraints on the baryon number of the B ball and the interaction, if the B
ball is the dark matter. We also discuss some unresolved properties of the B
ball.
