<p>A bellows for pressure vessel that would not rupture due to thermal expansion and contraction, avoiding accumulation of raw material. There is provided bellows (40) for pressure vessel adapted to realize ringlike sealing of open edge portion (11) of bottomed tubular vessel main body (10) in which a raw material is poured and an outer circumferential portion of dispersion board (30) choking up the open edge portion (11) so as to permit downflow of the raw material toward the bottom of the vessel main body (10). The bellows (40) is provided with flexure part (41) flexing radially so as to realize thermal expansion and contraction without caving for avoiding of accumulation of the raw material. The flexure part (41) is constituted of wavelike continuing concave curved surface (42) and convex curved surface (43).</p>
