1. An image decoding apparatus, including: an inverse conversion processing section into which is inputted encoded image data that is encoded for each region of a predetermined number of pixels by processing that includes motion compensation predictive coding processing that encodes a prediction error between a reference image having a predetermined time relationship and an image of an encoding object, and which is configured to obtain the prediction error or a restored image of the encoding object image by inverse processing of the encoding processing; a motion compensation section configured to obtain a restored image that restores an image before encoding processing for each of the regions of the predetermined number of pixels by adding the prediction error and the reference image that has undergone motion compensation; a storage section configured to store the restored image as a reference image; and a reference image acquisition section configured to read out the reference image from the storage section for addition processing of the motion compensation section, wherein, when an image of a processing object of the motion compensation section is encoded by an encoding mode that uses reference pixels having a number of pixels that is two times or more greater than a number of pixels of the region of the predetermined number of pixels, the reference image acquisition section obtains a reference image by reading out a reference image that is thinned out from the storage section and performing interpolation processing.