Disclosed is an optical pumping-type solid-state laser apparatus in which a semiconductor laser device is used as a light source for optical pumping. The solid-state laser apparatus includes first and second photodetectors. The former detects the amount of light emitted from the semiconductor laser device, and the latter detects the amount of laser light transmitted through a filter plate which has the same light-absorbance characteristics as that of the solid-state laser. In accordance with the detected results, a driving circuit drives the semiconductor laser device to obtain a laser beam with an appropriate output level and a temperature regulator regulates the temperature of the semiconductor laser device so that the wavelength of the laser light to be emitted therefrom is accurately adjusted to be the same as that of the light to be efficiently absorbed by the solid-state laser. The laser beam with the accurately adjusted wavelength is used for optically pumping the solid-state laser.