To provide an entry control system as well as an entry control method allowing for an easy entry of user, permitting a restriction to persons who have a legitimate right to enter a facility, an illuminating device (1) emits a modulated visible light signal 13 modulated by use of a door ID code into a preset illumination range, the modulated visible light signal 13 from the illuminating device (1) is received by a mobile terminal (2) portable by the user, where it is demodulated for wireless signal transmission, and the door ID code transmitted from the mobile terminal (2) is received by an authentication device (3), which judges whether or not the door ID code is legitimate, and generates an unlock command when the door ID code is judged to be legitimate, and a door (4) for a facility controlled of entry receives the unlock command from the authentication device (3), whereby it is unlocked.