The outer shape of a surface to be bonded of a first optical crystal member is formed as a shape in which the length in a direction parallel to an optical axis of the first optical crystal member differs from the length in a direction perpendicular to the optical axis of the first optical crystal member. The outer shape of a surface to be bonded of a second optical crystal member is formed as a shape coinciding with the outer shape of the surface to be bonded of the first optical crystal member or a shape obtained by enlarging or reducing the coinciding shape in an orientation in which an optical axis of the second optical crystal member and the optical axis of the first optical crystal member are adjusted to a prescribed angle.