A multi-wavelength surface plasmon laser that simultaneously emits surface plasmons having a large number of wavelengths and includes an active layer whose thickness changes with position, and a metal cavity whose length changes with position so that light of different wavelengths is emitted according to position. Surface plasmons are generated at the interface between a metal layer and a semiconductor layer in response to the light of different wavelengths. The surface plasmons having different wavelengths may be resonated in the metal cavity whose length changes with position and may be emitted to the outside.