Provided is a resonant cascaded difference frequency generator that is capable of improving the conversion efficiency of the second-order nonlinear optical phenomena by resonating the second harmonic wave of a pump light. The resonant cascaded difference frequency generator includes: a nonlinear medium, which receives a pump light and a signal light and then generates the second harmonic wave of the pump light through second harmonic generation, in a cascaded way generates a converted light of a difference frequency through difference frequency generation between the signal light and the second harmonic wave; and a resonant structure that resonates the second harmonic wave of the pump light on the basis of the nonlinear medium.