To inspect luminous characteristics under the state of the generation of a disturbance by generating the same disturbance as one generated under a severe temperature environment in a semiconductor laser element even by an inspection under room-temperature conditions.

The return beams of laser beams output from semiconductor laser element 10 itself are obtained by a half mirror 4 as a disturbance light causing the disturbance under an output state to the semiconductor laser element 10 to be inspected. Laser beams being output from semiconductor laser element 10 itself and being transmitted through the half mirror 4 are received while irradiating the semiconductor laser element 10 with the disturbance light. Data indicating the relationship of the quantity of the energy ([mW]) of the received laser beams and the quantity of an input current ([mA]) are collected by an IL measuring section 6. On the basis of the data, an output-characteristic abnormal decision section 7 conducts an inspection (a decision) in which an output-characteristic abnormality being latent in the semiconductor laser element 10 under the room-temperature state is actualized.