A gas concentration detection device includes: a gas concentration sensor having a gas sensor element that outputs an electric signal according to a gas concentration and a heater that heats the gas sensor element; a heater controller controlling energization and de-energization of the heater; a sensor controller having an ADC AD-converting the electric signal from an analog signal to a digital signal in synchronization with a sampling clock (fs) and detecting the gas concentration based on an output signal of the AD converter; and a timing adjuster shifting a switching timing of energization control from a conversion timing at which the AD converter performs the AD conversion.