PURPOSE: To enable a bellows-like cylindrical tank to be manufactured readily even at inconvenient mountain villages, by setting up a blank sheet into a container in stages including end folding, interlocking, edge bending, barrel R-groove pressure bonding and automatic wind-up roll sealing.

CONSTITUTION: A product 11 with the ends folded that has been electrically heated to be processed is formed into a cylinder with the ends interlocked, and after press bonding by an electric heating apparatus, the edges of the cylindrical barrel are bedned using a burner 27 of an automatic edge bending mechanism 24. While the cylinder is being rotated, an R-groove is formed in the barrel to give the cylinder itself tension and spring property, and a lid to which a flange or the like is fitted and bonded with an adhesive is sealed to the barrel using a wind-up roll sealing.