Tin monoselenide (SnSe), which belongs to group IV–VI monochalcogenides, has obtained significant attention in the field of photodetection owing to its ultrahigh carrier mobilities. However, the great challenges of preparing high-quality films and high-performance devices still need to be conquered. Herein, high-density continuous SnSe films were deposited on a Si substrate using magnetron sputtering technology, and a self-driven photovoltaic-type broadband photodetector from the visible light range (VIS) to the near-infrared (NIR) range based on SnSe/Si heterojunction was constructed. Owing to its high carrier mobility, narrow band gap structure, and strong internal electric field, the SnSe/Si heterojunction device exhibits an ultrafast response and high responsivity (R), which achieves a wide spectral response of 405–980 nm. Under zero bias voltage, the greatest R and detectivity (D*) of the heterojunction were 704.6 mA/W and 3.36 × 1011 Jones at 405 nm. Furthermore, the device had a fast response time (rise time) of 20.4 μs at 980 nm of illumination. This work provides a new strategy for the fabrication of high-performance, low-cost, and self-driven photodetectors.