The present invention provides an optical module able to reduce the power consumption thereof. The optical module, the package of which has a type of CAN or a co-axial shape, includes a Peltier device, a block, a laser diode (LD) and a photodiode. The block, mounting the LD on the side surface thereof, has a surface for reflecting the light emitted from the light-reflecting facet of the LD, and is mounted on the Peltier device. The photodiode, installed outside the Peltier device, receives the light emitted from the LD and reflected by the surface of the block. Since the photodiode is mounted outside the Peltier device, the cooling efficiency of the Peltier device may be enhanced, which saves the power consumption of the optical module.