An object of the present invention is to provide an optical apparatus, and a wavelength conversion laser light source, an image display apparatus, and a laser light source device adopting the optical apparatus, which ensure stable operations over a long period of use. The wavelength conversion laser light source includes: a non-linear optical crystal of an oxygen octahedral structure, having added thereto a metal ion in other components than a main component; a light source for projecting light into the non-linear optical crystal in an operation mode; and a refractive index recovery mechanism for carrying out a recovery operation for recovering a refractive index of said non-linear optical crystal as shifted overtime due to light projected into the non-linear optical crystal in the operation mode with an applied external energy into the non-linear optical crystal in a non-operation mode in which light is not injected to the non-linear optical crystal.