To provide a laser oscillator that has an oscillation wavelength in a visible region, and can enhance a conversion efficiency of photon output, and further suppress power consumption. The laser oscillator comprises a light emitting element formed on a substrate, and an optical resonator. The light emitting element includes a luminescent layer, an anode and a cathode, in which the luminescent layer is interposed between the anode and the cathode. The luminescent layer comprises a host material and a phosphorescent material, which is dispersed into the host material at a concentration of not smaller than 10 wt %. The anode and the cathode comprises a light transmitting property. In luminescence from the excimer state of the phosphorescent material, unidirectional light that intersects with the luminescent layer is amplified by the optical resonator.