A wedge-shaped jig (6) is inserted into a gap between a first substrate (21) and a second substrate (22) at a corner (221) of the second substrate (22) and separation of the attached first substrate (21) and second substrate (22) starts to proceed; then, a second suction pad (53) of a second suction portion (51), which is the closest to the corner (221), moves upward. Then, first suction pads (43) of first suction portions (41a), (41b), and (41c) sequentially move upward such that one side of the second substrate (22) separates from the stacked body. Although the second substrate (22) warps as the separation of the second substrate (22) proceeds, each of the plurality of first suction pads (43) elastically deforms. Therefore, the first suction pads (43) can be prevented from being detached from the second substrate (22), and the substrate (22) can be securely separated from the stacked body.