A receiver optical module that receives an optical signal and generating an electrical signal corresponding to the optical signal is disclosed. The module includes a photodiode (PD), a sub-mount, a pre-amplifier, and a stem. The sub-mount, which is made of insulating material, mounts the PD thereon. The pre-amplifier, which receives the photocurrent generated by the PD, mounts the PD through the sub-mount with an adhesive. The pre-amplifier generates an electrical signal corresponding to the photocurrent and has signal pads and other pads. The stem, which mounts the pre-amplifier, provides lead terminals wire-bonded with the signal pads of the pre-amplifier. The signal pads make distances against the sub-mount that are greater than distances from the other pads to the sub-mount.