A mobile radio communication system that enables to reduce its power consumption during a standby time without reception performance deterioration. The system contains a radio receiver for receiving a radio wave Witted from a base station to produce an input signal, and a supply power controller for controlling a supply power supplied to the radio receiver. An error detector detects an error generated in the control signal. A supply power controller controls to reduce a supply power to the radio receiver during a standby time according to appearance of errancy of the control signal. The error detector preferably detects to calculate an error rate of the control signal, and the supply power controller controls to change the supply power according to the result of comparison. The system may further contains a resetter for stopping the supply power reduction action of the supply power controller. The resetter is driven at call signal reception and transmission.