To provide a dancer roller device without impairing a buffer function and a long size object tension imparting function when carrying a long size object and a dancer roller lifting and lowering function for loading the long size object.

A dancer roller device includes a dancer roller 15 arranged between an upstream side carrying means and a downstream side carrying means on a carrying passage of a long size object W, absorbing a looseness quantity of the long size object W between them and imparting tension, a driving motor 30 for switching a path length of the long size object W by changing a position of the dancer roller 15 when carrying and loading the long size object W, and a dancer roller position changing means for changing the position of the dancer roller 15 by transmitting driving force from the driving motor 30. A one-way clutch 35 is arranged in the dancer roller position changing means for allowing the dancer roller 15 to move in the looseness direction of the long size object, and the driving motor 30 is caused to rotate in a direction such that the dancer roller 15 moves the one-way clutch 35 in the tension direction of the long size object when carrying the long size object W.