This paper presents a piezoelectric energy harvesting device applicable to wireless mouse (WM-PEH). Adding magnetic force to the excitation piezoelectric generating unit makes the impact better and more pronounced. The polygonal roller can increase the excitation frequency of the piezoelectric generating unit and broaden the energy collection range and capability of the WM-PEH. The theoretical and simulation analysis of WM-PEH was carried out in this paper. The effects of the length ratio of the exciter rod to the support frame and the circular impact area on the output characteristics of the prototype were discussed in the experiment. When the length ratio of the exciter rod and the support rod is 3:1, the activity increment of the exciter rod is the largest, and the maximum output voltage can reach 42 V and the maximum output power is 22.43 mW when it acts on a circular generator set with a radius of 1.5 mm. The design of the device is highly integrated with the wireless mouse that is widely used, and the piezoelectric energy harvesting mechanism and the wireless mouse are perfectly combined, which provides a scientific basis for the subsequent development of a self-powered wireless mouse.