In steady control, a shaft control unit (922) adjusts rotation speed of a first support shaft (31) to cause a first roll (R1) to have peripheral speed equal to predetermined conveyance speed by maintaining a sheet storage amount in a storage mechanism (5) in a first storage amount as a reference. In storage amount adjustment control, the shaft control unit (922) accelerates the rotation speed of the first support shaft (31) to increase the peripheral speed of the first roll (R1) higher than the conveyance speed, until the sheet storage amount in the storage mechanism (5) reaches a predetermined second storage amount that is larger than the first storage amount. A calculation unit (911) calculates an outer diameter of the first roll (R1) based on the conveyance speed when the steady control is performed, and calculates the outer diameter of the first roll (R1) based on the sheet thickness calculated from a decrease amount of the outer diameter of the first roll (R1) in the steady control when the storage amount adjustment control is performed.