The design of a wideband reflecting type linear-circular and linear-linear polarization converter in the THz frequency regime is described in depth in this work. The reflective polarizer unitcell seen here is made of a simple circular ring with two orthogonal cuts printed on top of a $\text{Si} 0_{2}$ substrate which is terminated with the ground. Post simulation results show a linearly polarized $((x/y)$ incident wave converted to its cross $(y/x)$ component in two frequency bands (7.19-11.12 THz and 15.28-15.78 THz) after reflection. The reflected wave would also be circularly polarized in the frequency bands (5.77-6.38 THz and 12.40-14.01 THz). The proposed structure has a unitcell periodicity of 0.1846 $\lambda_{\mathrm{L}}$ and an effective thickness of 0.0685 $\lambda_{\mathrm{L}}$, where $\lambda_{\mathrm{L}}$ is the lowest broadband frequency. For linear to cross conversion, the proposed design has a stable reaction up to 45°, and for linear to circular conversion, it has a stable response up to 30°. Authors are convinced that the proposed geometry has several advantages like simple, compact, and angular stable. It is used in real-time applications like polarization beam-splitters and time-domain spectroscopy, where these conversions are the primary concern. © 2021 IEEE.