A wavelength conversion device includes an excitation light source that generates excitation light, a laser medium that generates fundamental light by means of the excitation light, two resonator mirrors that are disposed with the laser medium being interposed therebetween and resonate the fundamental light, a wavelength conversion element that is disposed between the two resonator mirrors and wavelength-converts the fundamental light to harmonic light, and a drive unit that generates a pulse modulation signal to pulse-drive the excitation light source. The laser medium is formed of a material having a thermo-optical effect and a positive thermo-optical constant. The pulse modulation signal generated by the drive unit has an initial interval including a rising edge of a pulse and a remaining interval subsequent to the initial interval. An average signal intensity during the initial interval is higher than an average signal intensity during the remaining interval.