  We present the full nonlinear calculation of the formation of a Q-ball
through the Affleck-Dine (AD) mechanism by numerical simulations. It is shown
that large Q-balls are actually produced by the fragmentation of the condensate
of a scalar field whose potential is very flat. We find that the typical size
of a Q-ball is determined by the most developed mode of linearized
fluctuations, and almost all the initial charges which the AD condensate
carries are absorbed into the formed Q-balls, whose sizes and the charges
depend only on the initial charge densities.
