Distortion of the cross-sectional shape of a tube when producing a heat exchanger tube by cutting a continuous tube is prevented by forming cutting grooves in a strip material in advance by an upper and bottom cutter. The two side edges of the strip shaped member where stress will concentrate in the next tube forming step, the parts strongly bent, etc. are made thick, while the parts forming the belly surfaces of the tubes are made thin. At least four rollers are divided into two groups and arranged in a zigzag configuration. The continuous tube receives bending force in the forward and reverse directions between the group of rollers and is easily broken at the cutting grooves.
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