A radiation detection apparatus includes a radiation detection unit that detects a first intensity of a radiation that has been transmitted through an inspection target to generate a first measurement value, the inspection target being disposed between a radiation source that irradiates the radiation and the radiation detection unit, a transmission ionization chamber that detects a second intensity of the radiation that has not reached the inspection target to generate a second measurement value, the transmission ionization chamber having an enclosed structure, the transmission ionization chamber being disposed between the radiation source and the inspection target, the transmission ionization chamber including an entrance window through which the radiation enters the transmission ionization chamber and an exit window through which the radiation goes out of the transmission ionization chamber, and an operation unit that calculates a physical quantity of the inspection target.