To provide an optical system that lengthens the lifetime of a fiber, an optical system 13 guides light beams emitted from a plurality of light emitting parts ep into a single optical fiber 12, the plurality of light emitting parts ep are arranged to be aligned along a first direction d1, and the optical system 13 allows the light beams emitted from the plurality of light emitting parts ep to have different light collection centers which are offset from each other at least in a second direction d2.