PURPOSE: To make a cutting device incorporable into a high-speed strip manufacturing line, by having a cutter built in a drum so as to make it retractable with a compressed fluid, while constituting it so as to cut a strip in a gap between the cutter and an opposed roller.

CONSTITUTION: A cutter 14 built in a drum 13 is projected to a surface of the drum 13 with compressed air led into a projecting air chamber P1, coming into a cuttable condition in a gap with a roller 15, and the compressed air is led into a retracting air chamber P2, thus the cutter 14 is buried to the inside of the drum 13. With this constitution, intake timing of the compressed air into each of air chambers P1 and P2 and lifting timing of the roll 15 both are properly controlled with running velocity or the like of a strip material, and cutting takes place. Thus, such a cutting device as being incorporable into a high-speed strip manufacturing line is securable.