Terahertz (THz) bandpass filter (BPF) is one of important components in some detectors for astronomical observations. In this paper, a BPF with a relative bandwidth of 50% centered at 240 GHz is presented. This wideband BPF is made up of six ridged waveguide resonators and developed by silicon-based micro-electro-mechanical systems (MEMS) process. The transmission response of the filter is measured by a quasi-optical setup incorporating a sensitive superconducting mixer, and the result is in good agreement with the simulated one. Details of the design, simulation, and measurement are discussed in this paper.