  We study Q-ball formation in the expanding universe on 1D, 2D and 3D lattice
simulations. We obtain detailed Q-ball charge distributions, and find that the
distribution is peaked at Q^{3D}_{peak} \simeq 1.9\times 10^{-2}
(|\Phi_{in}|/m)^2, which is greater than the existing result by about 60%.
Based on the numerical simulations, we discuss how the Q-ball formation
proceeds. Also we make a comment on possible deviation of the charge
distributions from what was conjectured in the past.
