The present invention relates to a wireless mouse system. Particularly, the present invention relates to a wireless mouse system in which includes a controller, which controls a receiver and a flash memory device integrated into an interfacing device, can be performed function of the receiver and the flash memory device smoothly. A wireless mouse system comprises a wireless mouse and an interfacing device with a USB terminal, electrically communicated with a USB port of a information-displaying device. The interfacing device comprises a receiver receiving a signal data transferred wirelessly from the wireless mouse, and transferring the signal data to the information-displaying device, a flash memory device exchanging data with the information-displaying device through the USB terminal and a controller controlling the receiver and the flash memory device, and transferring optionally the signal of the receiver and the flash memory device to the information-displaying device.