To correctly control the moving amount of a fin material by preventing the variation of a tension value when adjusting the tension in a feedback tension unit for feeding the fin material to a working device while imparting the tension to the fin material.

This device is provided with: a tension imparting apparatus 201 for imparting the tension to the fin material 101 with a dancer roll 204 which is moved only in the vertical direction; an encoder 202 for measuring the quantity consumed of the fin material 101; and a controller 203 for moving the position of the dancer roll 204 so that the quantity consumed of the material per unit time becomes the target value on the basis of the results measured with the encoder 202. When the controller 203 performs feedback control so that the quantity consumed of the material per unit time becomes the target value on the basis of the results measured with the encoder 202, the variation of the tension value is prevented by allowing the dancer roll 204 to move only in the vertical direction (z-axis direction).