To provide a corrugating device capable of safely and smoothly corrugating a flat sheet into desired shape and size by one engaging operation with a simple structure.

The horizontal movements of abutting and separating are performed by a male die projecting part 2 mounted on a male die 10 to be vertically moved, a pressing-down plate 9 holding a flat sheet, and female die groove parts 3a and 3b mounted on moving dies 6a and 6b respectively by cam drivers 4a and 4b, and a corrugation shape is formed by the female die groove parts 3a and 3b fitting with the male die projecting part 2. The device is equipped with a movable cam guide mechanism 8 not making the moving die 6b with a positioning groove part M on the female die groove part 3b separate until the male die projecting part 2 is released from the upper surface of a corrugation after the completion of the working. Continuous corrugation is performed while repeating that the corrugated shape formed previously is engaged with the positioning groove M.