An optical module 10 according to the invention is comprised of: a substrate 11; a laser diode array 14 implemented on said substrate in an array; a driver IC 15 implemented on said substrate and electrically connected to each of surface emitting semiconductor laser elements of the laser diode array 14; an optical connector unit 12 for holding a plurality of optical fiber 16 in an array, wherein the optical connector unit 12 is fixed to the substrate 11 in a location where center of each single end of said plurality of optical fiber and center of each light injecting region are aligned with each other; and a cover 13. The optical connector unit 12 includes two guide-pin holes 12b on two opposite sides of a plurality of fiber holding hole 12a. Two alignment marks 50 are provided on a surface 11a of the substrate 11, which are visually recognizable through each of the guide-pin holes 12b, and function as alignment reference of said optical connector unit 12.