A radiation inspection apparatus includes a radiation source, a measurement radiation detecting unit being a rectangle having a long side, and a reference radiation detecting unit that is disposed between the radiation source and an inspection target, the reference radiation detecting unit being disposed near a path of a radiation from the radiation source to the measurement radiation detecting unit not to interrupt the radiation from the radiation source to the measurement radiation detecting unit. An intensity of the radiation source are corrected by calculating a change value of the intensity and the intensity distribution from an output of the reference radiation detecting unit and by correcting the output of the measurement radiation detecting unit based on the change value.