An optical module for supplying pump light for amplifying to-be-amplified light includes an pump light source, optical coupling means, and an optical guide section. The optical guide section optically connects the pump light source and the optical coupling means, and propagates the pump light from the pump light source, in multi-transverse-mode. The optical coupling means output the pump light from the optical guide section in multi-transverse-mode, and at least one of (i) at least one of end faces where the optical guide section and the optical coupling means are connected, (ii) an area between the end faces, and (iii) the optical guide section, has a loss medium of which transmission loss is greater in a wavelength of the to-be-amplified light than in a wavelength of the pump light. By this, an optical module which can stably supply the pump light to the optical amplification fiber can be provided.