A wave plate 1 according to an embodiment includes a first birefringent substrate 10 including a first main surface and an optical axis 13 in a first direction; a second birefringent substrate 20 disposed over the first birefringent substrate 10 and including a second main surface and an optical axis 23 in a second direction; and a third birefringent substrate 30 disposed over the second birefringent substrate 20 and including a third main surface and an optical axis 33 in a third direction. The first birefringent substrate 10 and the second birefringent substrate 20 are made of the same kind of birefringent material. The first main surface, the second main surface, and the third main surface are disposed in parallel to one another. The first direction and the second direction are parallel to the first main surface and the second main surface.