Provided is an unwinding device for unwinding a sheet from a sheet roll, the sheet roll being inserted onto the device. The unwinding device includes a shaft, a first rotating member and a second rotating member which are inserted onto the shaft, configured to be rotatable with rotation of the sheet roll, the sheet roll being inserted onto the first rotating member and the second rotating member, a first elastic member disposed between the first rotating member and the shaft, the first elastic member being configured to provide first back tension to the sheet when the first rotating member rotates, a second elastic member disposed between the second rotating member and the shaft, the second elastic member being configured to provide second back tension to the sheet when the second rotating member rotates, and a back tension controlling member disposed between the second elastic member and the shaft.