In a digital receiver, a noise attenuation and signal magnitude mapping variable amplifying unit includes a filter and an amplifier, amplifies and band-bass filters an analog signal and attenuating white noise and an interference signal other than a band signal. An ADC performs sub sampling on a carrier frequency of a desired signal and performs oversampling on the band of the desired signal by using a sampling frequency to convert the analog signal which has passed through the noise attenuation and signal magnitude mapping variable amplifying unit into a digital signal of a direct conversion frequency band or an intermediate frequency band. The ADC has a dynamic range for processing both the desired signal and an undesired signal adjacent to the desired signal. A digital signal processing unit converts a signal frequency of the digital signal or digital-filters an undesired signal within the digital signal and processes the digital signal by digitally adjusting a gain.