An image decoding device and an image coding device are each capable of using spatial dependence across a boundary between slices to smoothly execute parallel processing. The image decoding device includes: a first decoding unit (801) decoding a block in a first slice; a second decoding unit (802) decoding a block in a second slice; and a first storage unit (811) storing inter-slice neighboring information (i) generated by decoding a boundary block included in the first slice and adjacent to the second slice and (ii) referenced when a boundary neighboring block included in the second slice and adjacent to the boundary block is decoded. The first decoding unit (801) generates the inter-slice neighboring information by decoding the boundary block and stores the generated information into the first storage unit (811). The second decoding unit (802) decodes the boundary neighboring block by reference to the stored inter-slice neighboring information.