An optical module is composed of a plurality of optical elements to emit or receive light rays having wavelengths different from each other, and a plurality of optical members arranged in correspondence with the plurality of optical elements respectively. The plurality of optical members each of which includes a mirror section to transmit a predetermined transmission band wavelength light ray while reflecting a predetermined reflection band wavelength light ray, and a lens section located opposite the corresponding optical element. The plurality of optical members are positioned and disposed in such a manner that the respective lens sections thereof collimate or converge the light rays to be emitted or received by the plurality of optical elements respectively, while the respective mirror sections thereof multiplex or demultiplex the light rays to be emitted or received by the plurality of optical elements respectively.