A method of manufacturing a plasmon generator includes the steps of forming an accommodation part and forming the plasmon generator to be accommodated in the accommodation part. The step of forming the accommodation part includes the steps of: forming a dielectric layer having an upper surface; etching the dielectric layer by using an etching mask and thereby forming a groove in the dielectric layer; and forming a dielectric film in the groove. The groove has first and second sidewalls and a bottom. Each of the first and second sidewalls forms an angle in the range of 0° to 15° relative to the direction perpendicular to the upper surface of the dielectric layer. The dielectric film includes a first portion interposed between the first sidewall and the first side surface, and a second portion interposed between the second sidewall and the second side surface.