Growth kinetics of tetragonal hen egg-white lysozyme crystals under high pressures was studied by in situ measurements. Normal growth rates of {1 1 0} and {1 0 1} faces were measured under 0.1, 50, and 100 MPa. The solubilities under high pressure enabled us to evaluate supersaturation under high pressure. We found that both growth rates decreased with pressure under the same supersaturation. This means that the surface growth kinetics significantly depends on pressure. The birth and spread model was applied to understand the pressure effects on the growth kinetics. It was found that the increase in the average ledge surface energy of the two-dimensional nuclei with pressure explained the decrease in the growth rare.