A wavelength conversion module includes: a first fundamental wave propagation optical fiber for propagating a fundamental wave emitted from a laser light source; a first wavelength conversion element, optically connected to the first fundamental wave propagation optical fiber, for converting the fundamental wave emitted from the first fundamental wave propagation optical fiber into a harmonic wave; and a first harmonic propagation optical fiber, optically connected to the first wavelength conversion element, for propagating the harmonic wave emitted from the first wavelength conversion element, wherein the core diameter of the first harmonic propagation optical fiber is 0.5 to 0.9 times as large as the core diameter of first fundamental wave propagation optical fiber.