A radiation detection device includes a radiation detection sensor, a first integration section, a second integration section and a determination section. The first integration section obtains a first integration value by integrating values expressed by signals output from the sensor over a predetermined period of time. The second integration section obtains a second integration value by integrating amounts of change per specific time duration in values expressed by the signals output from the sensor over the predetermined period of time. The determination section determines whether or not radiation has been detected by the sensor based on a ratio of the first integration value to the second integration value.
