A keyless entry system for remotely controlling a door and a window of a vehicle includes: a remote control key that stores a plurality of function codes, selects a function code corresponding to an on-duration time of a lock switch or an on-duration time of an unlock switch, modulates the selected function code to a wireless signal, and transmits the wireless signal; and a receiving device that receives the wireless signal, demodulates the wireless signal into the function code, and outputs a door control signal or a window control signal according to the modulated function code, where the function code is divided into a basic function code field and a window function code field.