A fastening device includes: a support portion including a first end portion, and a second end portion, and a central portion between the first and second end portions; a first pulley, a second pulley, and a third pulley rotatably disposed on the central portion, the first end portion, and the second end portion, respectively; a first connection portion and a second connection portion respectively rotatably disposed on the first and second end portions and respectively connected to the second and third pulleys; a first fastening tool and a second fastening tool respectively connected to the first and second connection portions; and a motor connected to the first pulley, wherein a force generated by the motor and provided to the first pulley is at least partially transmitted to the second and third pulleys to vary a distance between the first and second fastening tools.