[Task] To provide a semiconductor light emitting element capable of emitting light beams with wavelengths in a plurality of wavelength ranges with a high optical output, a driving method of a semiconductor light emitting element capable of making a semiconductor light emitting element that can emit light beams with wavelengths in a plurality of wavelength ranges operate with a high optical output, a light emitting device, and a small and high-performance optical pulse tester using the light emitting device.[Means for Resolution] In a driving method of a semiconductor light emitting element with a configuration in which an active layer 13a with a gain wavelength λ1 of about 1.55 μm and an active layer 13b with a gain wavelength λ2 of about 1.3 μm are optically coupled along the guiding direction of light and are disposed in series in order of the length of the gain wavelengths λ1 and λ2 and a diffraction grating 20 with a Bragg wavelength of the short gain wavelength λ2 is formed near the active layer 13b with the short gain wavelength λ2 and near a butt-joint coupling portion 19 between the active layers 13a and 13b, an upper electrode provided above the active layer 13b is short-circuited to a lower electrode provided on a bottom surface of a semiconductor substrate so that a leakage current does not flow into the active layer 13b when a driving current is applied to the active layer 13a.