A surface emitting laser includes a lower reflector, an active layer, and an upper reflector that are arranged in that order; an air gap provided between the active layer and the upper reflector; and a slab provided on an optical path of the air gap and having a refractive index that is higher than a refractive index of the air gap. A position of at least one of the upper reflector and the lower reflector in an optical axis direction is changed to change a wavelength of emitted light. In the case where the position of the upper reflector is changed, a center of the slab in the optical axis direction is located between any antinode of a standing wave formed in the air gap and a node of the standing wave that is adjacent to and on an upper-reflector side of the antinode.