To make a terahertz wave generation system capable of easily illuminating terahertz wave on an arbitrary position and to easily realize the system for practical use by effectively using existing systems and devices, the terahertz wave generation system has: a two-wavelength oscillation laser device capable of simultaneously oscillating laser light having two wavelengths and varying the wavelengths; an optical fiber that transmits laser light having two wavelengths, which has been output from the two-wavelength oscillation laser device; and wavelength conversion means for generating terahertz wave by difference frequency generation using the laser light having two wavelengths, which has been transmitted by the above-described optical fiber.