Even in a case where radiation imaging is performed using a grid, data lack which occurs at a time of radiation detection is appropriately corrected. An FPD controller 105 obtains data of an image captured by detecting radial rays. A data lack ratio calculation unit 111 calculates data lack ratios in the image data. A fitting unit 112 performs fitting so that a model function representing the data lack fits the data lack ratios. A correction processing unit 113 corrects the image data in accordance with the model function obtained by the fitting.