A structure for a nacelle cover connection portion of a wind turbine generator includes a lengthy first angled member fixed to an inside surface of a nacelle cover and forming an upper end portion of a side wall panel; and a lengthy second angled member fixed to the inside surface and forming a lower end portion of a roof panel. An upper surface of the first angled member and a lower surface of the second angled member are aligned with and fixed to each other. A covering portion covering the upper end portion from the outside of a nacelle is provided at a predetermined interval from the same and integral with the lower end portion so as to protrude to the outside of the nacelle cover farther than the lower end portion. A packing is interposed between the upper and lower surfaces.