A light emitting device includes: a first light emitting element having a light emitting surface; an optical member having a lower surface, a first reflecting surface inclined to the lower surface, transmitting part of a first light emitted from the light emitting surface, and reflecting the rest upward, and a second reflecting surface located farther from the light emitting surface than the first reflecting surface and reflecting part or all of the first light passing through the first reflecting surface; and a photodetector located below the optical member and having a top surface provided with one or a plurality of light receiving regions including a first light receiving region configured to receive the first light reflected by the second reflecting surface. In a top view, part or all of the first light receiving region overlaps part or all of the first reflecting surface.