Radiation images, which are obtained while reciprocally moving a scattered radiation removing means, are efficiently corrected. An image processing apparatus performs shading correction and gain correction on a radiation image which is obtained by detecting radiation that passes through a subject and is detected by a radiation detector while reciprocally moving the scattered radiation removing means, using a reference image. An irradiation control means controls irradiation of radiation during obtainment of the reference image such that irradiation is ceased after the scattered radiation removing means is reciprocally moved for k periodic reciprocal motions (k is an integer greater than or equal to 1) from initiation of irradiation. Meanwhile, irradiation of the radiation during obtainment of the radiation image is controlled such that irradiation is ceased after the scattered radiation removing means is reciprocally moved for m periodic reciprocal motions (m is an integer greater than or equal to 1).