We develop a variational quantum Monte Carlo method in many-body systemss employing nonlocal pseudopotentials. An application is made for the Si atom. One-body Jastrow term is introduced to adjust the one-body charge density calculated from the local density functional approximation(LDA). Minimizing the total energy with only the two-body term, we find that the Jastrow factor lowers the energy by 1.51 eV compared to the LDA value. However, this calculated energy is higher by 0.53 eV than the configuration interaction result of -103.60 eV.