To provide a nacelle roof structure of a wind turbine generator, where the nacelle roof structure is capable of reducing stress concentration on joints of a roofing member divided into multiple parts to accommodate growing size of a nacelle as well as improving transport efficiency of the roofing member. A nacelle roof structure of a wind turbine generator, with a top face of a nacelle being covered with a plate-type roofing member (30), in which the roofing member (30) has a joining structural portion (32) in which roof shingles (31) that divide the roofing member into a plurality of parts in a main-shaft direction are combined and plate couplings provided at opposite ends in the main-shaft direction are fastened together by being laid one on top of another; and two or more of the roof shingles (31) are equal in cut length in the main-shaft direction.
