To provide an irradiation apparatus capable of carrying out optical irradiation while preventing the deformation and/or degradation of an irradiated object.

In a multi-emitter semiconductor laser 1, the displacement (smile S1) of each semiconductor laser device in the direction (Z-axis direction) orthogonal to the arrangement direction (Y-axis direction) thereof is made not larger than the length (height H1) thereof in the Z-axis direction. The reduction in the power density of the irradiating light is suppressed as compared to the conventional case wherein the displacement is larger. Further, higher precision optical irradiation can be carried out for a desired irradiation region.