An oscillator housing includes a main body unit that is shaped into a frame and formed of a metallic material and a cover unit that is formed of a metallic material to cover openings of the main body unit, and has an outer wall that has an arc cross section perpendicular to the optical axis and extends in the optical axis direction and side walls that are connected to the both ends of the outer wall in the optical axis direction. When the cover unit is fixed to the main body unit with a fixing member, the outer wall having an arc shape is configured such that force is generated in the height direction towards the outside of the oscillator housing on the connecting portion of the cover unit with the main body unit.