The evaporation phenomenon of metals is simulated by using the lattice Boltzmann method (LBM). It is the objective to obtain the evaporation rate of metals in an inert gas in high temperature. The relaxation time for the BGK type relaxation of the LBM is derived microscopically. The evaporation rate is arranged with the reduced pressure, the ratio of saturated vapor pressure and total pressure, and the Knudsen number. The dependence of the evaporation rate on pressure of surrounding gas is compared with reported experimental results and validity of the simulation is confirmed. The potential model of metal atoms at a collision and the discrete velocity model of the LBM are evaluated and the simulated evaporation rate hardly depends on them. The evaporation rates at various kinds of surrounding gas and evaporating metal gas are calculated, and the decrease of the evaporation rate depends on momentum transfer in collision, not on collision cross sections.