A compact unitraveling-carrier photodiode (UTC-PD) module with a WR-8 rectangular waveguide output port for operation in the F-band (90-140 GHz) has been developed. A resonating matching circuit integrated with a UTC-PD and a microstrip-line-to-rectangular-waveguide transformer are designed to have high output powers with a wide bandwidth covering the F-band. The module size and configuration are equivalent to those of conventional optoelectronic devices, which enables the use of standard assembly technology. The fabricated module exhibits a record millimeter-wave output power of 17 mW at 120 GHz for a bias voltage of -3 V. The 3-dB bandwidth is as wide as 55 GHz, which fully covers the F-band. An optical input stress test at a photocurrent of 10 mA performed to confirm the long-term stability of the module showed that the dark current stays below 1 μA for more than 4000 hours.