A highly miniaturized on-chip $180^{circ}$ hybrid employing periodic ground strip structure (PGSS) was realized on a silicon radio frequency integrated circuit. The PGSS was placed at the interface between $SiO_2$ film and silicon substrate, and it was electrically connected to top-side ground planes through the contacts. Owing to the short wavelength characteristic of the transmission line employing the PGSS, the on-chip $180^{circ}$ hybrid was highly miniaturized. Concretely, the on-chip $180^{circ}$ hybrid exhibited good radio frequency performances from 37 GHz to 55 GHz, and it was 0.325 $mm^2$, which is 19.3% of a conventional $180^{circ}$ hybrid. The miniaturization technique proposed in this work can be also used in other fields including compound semiconducting devices, such as high electron mobility transistors, diamond field effect transistors, and light emitting diodes.