A wavelength conversion laser (100) comprises a solid-state laser having a cavity and a wavelength converting element (6) disposed in the cavity. The solid-state laser contains two or more crystals (4, 5) of different kinds and oscillates solid-state laser beams having wavelengths. The wavelength converting element (6) converts the solid-state laser beams into beams including second harmonics andsum-frequency waves to simultaneously produce the second harmonics and the sum-frequency waves. Thus, the wavelength conversion laser (100) outputs a converted wavelength light having a wide spectrumwidth and having a low coherency and stably oscillates a laser beam of high output power with high efficiency.