A wireless signal receiving device with prompt wake-up function is disclosed for receiving serial data transmitted from computer peripherals. The device includes a RF signal receiving module, a bridge module and a USB module, which can operate in normal mode, first idle mode, second idle mode or search mode. When the device is in the first idle mode, it still receives serial data normally. When the device is in the second idle mode, the device can change to the search mode periodically to search whether there is new transmitted data. The main drawback of not being promptly waken up when the conventional wireless signal receiving device is in idle mode is improved through the disclosed device and the two idle modes.