1. An accumulation device, comprising:an infeed unit configured to feed in a substrate;
an outfeed unit configured to feed out the substrate;
a tensioning unit disposed toward upstream in a transporting direction of the substrate between the infeed unit and the outfeed unit, the tensioning unit being configured to apply predetermined tensile force to the substrate;
an accumulation unit disposed downstream of the tensioning unit in the transporting direction of the substrate between the infeed unit and the outfeed unit, the accumulation unit being configured to accumulate a surplus of the substrate generated by a difference between a substrate infeed rate of the infeed unit and a substrate outfeed rate of the outfeed unit; and
a controller configured to control an operation of each of the infeed unit, the outfeed unit, and the accumulation unit,
the tensioning unit includes a plurality of rotatable fixed rollers spaced from each other and arranged in parallel to each other, and at least one rotatable movable roller disposed in parallel to the fixed rollers, the at least one rotatable movable roller being movable toward and away from the fixed rollers, the substrate being transported while being wound alternately around the fixed rollers and the at least one movable roller,
the tensioning unit is configured to apply the predetermined tensile force to the substrate by a force acting onto the movable roller in a direction away from the fixed rollers, and
the controller is configured to maintain a constant position of the movable roller with respect to the fixed rollers of the tensioning unit.