An input signal detecting apparatus and method in a digital receiver is provided. The input signal detecting apparatus includes an outer AGC for receiving an input signal and thereby controlling gains of RF and IF AGC amplifiers and generating an IF AGC gain value; an inner AGC for receiving the input signal and thereby generating an inner AGC gain value; and an input signal detector for receiving the input signal, a predetermined input signal power reference value, the IF AGC gain value and the inner AGC gain value and thereby generating a signal for representing a condition of stability of an input signal and a signal for representing a condition of existence of an input signal, thereby making it possible to reduce the channel information scanning time and determine a time at which an after-edge recoverer should be activated, by using the condition of existence of an input signal and the condition of stability of an input signal.