CP violation in the semileptonic top decay in two-Higgs doublet model

CP violation in semileptonic top-quark decay is investigated by exactly using one charged- and three neutral-Higgs bosons obtained by solving the Higgs mass matrix in two-Higgs doublet model. The CP-violating up-down asymmetry of leptons from $W$ boson decays is shown to be $1 \times 10^{-4} - 4 \times 10^{-3}$fortheregionof${\rm tan} \beta \ll 1$,where${\rm tan} \beta $ is the ratio of vacuum expectation values for the two neutral Higgs bosons.