An excluder (90) inserted into a human body for surgery. The excluder body (91) of the excluder (90) is formed by compressing and shaping a water-absorbing dilatant material so that expansion stress in the direction opposite the direction of the compression remains therein and so that the value of the residual expansion stress varies from portion to portion. Weld sections (92) consisting of a thermoplastic resin are provided to the surfaces (side surfaces (91b, 91d)) facing the direction in which the residual expansion stress is acting. When supplied with water, the excluder body (91) swells large at the center portion (C) thereof at which the expansion stress is high and the excluder body (91) swells small at both the end portions (E) thereof at which the expansion stress is low. The weld sections (92) do not extend, and this controls the shape of the excluder (90) so that, after swelling, the excluder has a curved shape.
