To provide a keyless entry system which can prevent its erroneous operation of door locking/unlocking.

According to the keyless entry system, an opening/closing signal transmitting section 110 is comprised of an opening/closing frequency memory device 112 which stores therein a frequency in a frequency band allotted to broadcasting but unassigned to broadcasting at a current location, as an opening/closing frequency, a modulator 114 which carries out modulation of a carrier wave with the opening/closing frequency, based on an opening/closing signal, and a radio transmitter 115 which transmits the opening/closing signal with the opening/closing frequency output from the modulator 114 by radio to an opening/closing signal receiving section 130. The opening/closing signal receiving section 130 is comprised of an opening/closing frequency memory device 142 which stores therein the opening/closing frequency, a radio receiver 130 which receives the opening/closing signal from the opening/closing signal transmitting section 110 by radio, by setting the opening/closing frequency to a tuned frequency, and a demodulator 132 for demodulating the received opening/closing signal, and a door locking/unlocking device 135 for locking/unlocking a door lock 123.