An image processor includes an inter-superimposed-image deformation acquisition unit configured to acquire deformation information between superimposed images included in a multiple image in which images of a subject are superimposed, an image deformation unit configured to generate at least two deformed images by performing deformation processing with respect to the multiple image at least twice to be geometrically deformed based on the acquired deformation information between superimposed images, and a signal intensity relationship acquisition unit configured to acquire signal intensity relationship information indicative of a relationship between signal intensities of the superimposed images included in the multiple image. The image processor further includes a signal processing unit configured to perform addition processing of the at least two deformed images generated from the deformation processing by using the acquired signal intensity relationship information.