The present disclosure relates to an image decoding device capable of recognizing performance necessary for decoding more accurately and a method. Coded data of image data and decoding load definition information for defining a magnitude of a load of a decoding process of a partial region of an image of the image data are acquired; decoding of the acquired coded data is controlled based on the acquired decoding load definition information; and the acquired coded data is decoded according to the controlling. The present disclosure can be applied to an information processing device such as an image coding device that scalably codes image data or an image decoding device that decodes encoded data obtained by scalably coding image data.