A wavelength conversion laser apparatus including: a laser light source emitting primary wavelength light; a non-linear optical crystal including: a light waveguide region having a first refractivity, the light waveguide region receiving the primary wavelength light to output as secondary wavelength light; and a clad region adjacent to the light waveguide region, the clad region having a second refractivity lower than the first refractivity, wherein at least the light waveguide region has a periodically domain-inverted structure formed such that a domain-inverted period varies in a direction perpendicular to an incident axis of the primary wavelength light; and a mover moving the non-linear optical crystal to change the domain-inverted period on a path where the primary wavelength light incident on the light waveguide region passes.