  We consider the baryon number generation by charge transport mechanism in the
electroweak phase transition taking properly into account thermal fluxes
through the wall separating true and false vacuum in the spatial space. We show
that the diffusion from the true vacuum to the false one has a large
diminishing effect on the baryon number unless the wall velocity is near to,
but less than, the speed of sound in the medium and the ratio between the
collision rate and wall thickness is about 0.3. The maximum net baryon density
generated is $\rho_B/s\simeq 0.2\times 10^{-10}$, where $s$ is the entropy
density of the Universe. If the wall proceeds as a detonation, no baryon number
is produced.
