PURPOSE: To obtain a petal type finned tube efficiently at low cost by winding a plain tube with a corrugated fin material while rotating the plain tube and a corrugating device equipped with pins and plunger punches intermittently.

CONSTITUTION: The plain tube after being coated with solder by a solder coating device 53 is inserted into the hollow shaft 16 of the corrugating device consisting of a die rotating cylinder 12 wherein plural pins 26 are implanted annularly on its side end surface and a die rotating cylinder 25 equipped with two plunger punches 18a and 18b operated by air cylindes 19a and 19b. Then said rotating cylinders 11 and 12 are both rotated and the punches 18a and 18b are intruded along die guide grooves 21 and 25 to corrugate the fin blank material supplied onto the pins 26. Simultaneously, the corrugating device and plain tube are rotated and moved intermittently and relatively to wind the formed fin blank material around the plain tube, which is then heated for soldering, obtaining the petal type finned tube.