1. An image decoding device which decodes hierarchically encoded data, restores motion information of a decoding target layer, and restores an image of the target layer by using a predicted image generated by motion compensation prediction based on the restored motion information, comprising: a merge candidate derivation circuit configured to derive a plurality of merge candidates in a target prediction unit for generating the predicted image on the target layer, wherein the merge candidate derivation circuit includes, as one of individual merge candidate derivation means, an inter-layer candidates derivation circuit configured to derive a merge candidate called an inter-layer merge candidate, by using a motion information which is decoded and associated with a predetermined region on a reference layer, wherein the predetermined region is a position corresponding to a lower right position derived by adding an offset, having a lower right direction, to a pixel position on a reference layer calculated by referring to a top-left pixel position of the target prediction unit, wherein the merge candidate derivation circuit further includes, as one of the individual merge candidate derivation means, a spatial merge candidate derivation circuit configured to derive a merge candidate called a spatial merge candidate, by using motion information of positions of an upper right part, a lower left part, and an upper left part of the target prediction unit, wherein a plurality of merge candidates derived by the merge candidate derivation circuit include the inter-layer merge candidate and the spatial merge candidate, wherein a recording position of the motion information, which is decoded and associated to the predetermined position, is represented by ((xC0//N)*N, (yC0//N)*N), where (xC0, yC0) is the predetermined position and N is positive integer value.