A receiver capable of performing optimum automatic gain control responsive to a peak factor of an input signal before subjected to A/D conversion is provided in a simple configuration. A peak detector 104 is placed at the later stage of a variable gain amplifier 102, two power determiners 107 and 108 different in threshold value are used, and the amplitude density is determined in three areas separated by two threshold values PDETL and PDETH, whereby it is made possible to identify the input signal having a peak factor different in modulation system and perform optimum gain control without A/D conversion of the input signal.