A receiving device which receives radio waves intermixing desired waves and interfering waves so as to carry out automatic gain control and demodulation, the receiving device comprising: a low noise amplifier configured to amplify a received signal; an intermediate frequency converter configured to convert the received signal output from the low noise amplifier into an intermediate frequency signal by use of an local oscillator frequency; an analog variable gain function part configured to amplify the intermediate frequency signal with a first gain; an A/D converter configured to carry out analog-to-digital conversion on the intermediate frequency signal amplified with the analog variable gain function part, so as to output a first digital signal; a channel selecting filter configured to filter out a frequency band of a specific channel from the first digital signal in order to attenuate interfering waves so as to produce a second digital signal; a digital variable gain function part configured to amplify the second digital signal of the specific channel with a second gain; a first RSSI part configured to detect a first received signal strength from the first digital signal output from the A/D converter; a second RSSI part configured to detect a second received signal strength from the second digital signal of the specific channel output from the channel selecting filter; a comparison controller configured to determine an occurrence of interfering waves when a difference between the first received signal strength and the second received signal strength exceeds a second threshold, and further configured to calculate the first gain applied to the analog variable gain function part based on a part of the first received signal strength exceeding a first threshold and to calculate the second gain applied to the digital variable gain function part based on the first gain set to the analog variable gain function part when the difference between the first received signal strength and the second received signal strength exceeds the second threshold; and a demodulator configured to demodulate the second digital signal amplified with the digital variable gain function part. a low noise amplifier configured to amplify a received signal; an intermediate frequency converter configured to convert the received signal output from the low noise amplifier into an intermediate frequency signal by use of an local oscillator frequency; an analog variable gain function part configured to amplify the intermediate frequency signal with a first gain; an A/D converter configured to carry out analog-to-digital conversion on the intermediate frequency signal amplified with the analog variable gain function part, so as to output a first digital signal; a channel selecting filter configured to filter out a frequency band of a specific channel from the first digital signal in order to attenuate interfering waves so as to produce a second digital signal; a digital variable gain function part configured to amplify the second digital signal of the specific channel with a second gain; a first RSSI part configured to detect a first received signal strength from the first digital signal output from the A/D converter; a second RSSI part configured to detect a second received signal strength from the second digital signal of the specific channel output from the channel selecting filter; a comparison controller configured to determine an occurrence of interfering waves when a difference between the first received signal strength and the second received signal strength exceeds a second threshold, and further configured to calculate the first gain applied to the analog variable gain function part based on a part of the first received signal strength exceeding a first threshold and to calculate the second gain applied to the digital variable gain function part based on the first gain set to the analog variable gain function part when the difference between the first received signal strength and the second received signal strength exceeds the second threshold; and a demodulator configured to demodulate the second digital signal amplified with the digital variable gain function part.