An allowable temperature range satisfying phase matching conditions of a wavelength conversion device is widened. A wavelength conversion light source includes a semiconductor laser diode device (1) applied with an antireflection film (3), a lens (4) arranged opposite to the semiconductor laser diode device (1), an optical fiber (5) having a Bragg grating (6) arranged in a core thereof, and a wavelength conversion device (8) formed of a nonlinear optical crystal on which light from the semiconductor laser diode device (1) is incident. In the wavelength conversion light source, the semiconductor laser diode device (1) oscillates in coherent collapse mode.