Provided is a wind power generator that reduces the amount of heat input into a nacelle from the outside of the nacelle due to the solar radiation, and that improves the heat dissipation performance from the inside of the nacelle to the outside air. In a wind power generator in which a driving mechanism and power generation mechanism that are connected with a rotor head, to which wind-turbine blades are attached, are accommodated and installed in a nacelle, an outer wall surface of the nacelle is provided with, on at least a part of the wall surface where no direct sunlight is radiated, a heat-dissipation-resistance reducing portion that uses a member having a higher thermal conductivity than that of a peripheral wall member.