PURPOSE: To continuously and efficiently manufacture can bodies for threepiece cans using a comparatively thin metallic sheet having restraining flexibility while completely joining them with high out-of-roundness of the section thereof.

CONSTITUTION: In order to continuously form cylindrical can bodies while transporting a belt like flat metallic sheet, after the metallic sheet 100 is feeded, both side edges are opposed and erecled by a joining part raising means 14, the central flat part is gradually bent by a cylindrical forming means 15, and after the metallic sheet is formed into a longitudinal cylindrical shape that the diameter including superposed both side edge part to be joined is the major axis, the superposed both side edge part is joined by a joining means 16. Thus, the formed continuous longitudinal cylindrical body is pressurized to be corrected to have nearly round cross-section by a correcting means 17 so that the diameter including the joined part is the minor axis and the corrected continuous cylindrical body 101 is cut into a desired length by a cutting means 18.