An optical module having a second connector unit mounted on the bottom of a first connector unit to reduce the size of the radiation member and the optical module. The optical module includes a first connector unit, a radiation member provided on a first side of the first connector unit to support the first connector unit and radiate heat, a second connector provided on the first connector unit to electrically connect the first connector unit to a PCB, and a fastening member provided on surfaces of the first and second connector units, which face each other, to fasten the first and second connectors to each other. The optical module is advantageous reduces the size of the radiation member and renders a more compact optical module.