Involving a step for acquiring a bit stream that includes a flag indicating the segmentation information for block units; a step for decoding and acquiring a top flag that is attached to a top block belonging to a hierarchy with a smaller depth than the depth (N) of a hierarchy and that indicates the quadtree segmentation information for the aforementioned top block; a step for decoding and acquiring a first bottom flag that is attached to a first bottom block from among bottom blocks belonging to the aforementioned hierarchy depth (N) and that indicates the quadtree segmentation information for the aforementioned first bottom block; a step for setting a predetermined first value as a second bottom flag that indicates the quadtree segmentation information for a second bottom block belonging to the aforementioned hierarchy depth (N) in cases in which the already acquired aforementioned top flag and the aforementioned plurality of first bottom flags are a specific combination, and for decoding and acquiring the aforementioned second flag in cases in which the previous are not the aforementioned specific combination; and a step for generating the decoded image signal for the aforementioned blocks in accordance with the aforementioned top flag and first and second bottom flags.