According to an aspect of the present invention, there is provided a sheet processing device including a first teeth portion, a second teeth portion that clamps and binds a sheet bundle with the first teeth portion, a first support portion supporting the first teeth portion, a shaft, and a second support portion supporting the second teeth portion. The second support portion includes first and second arm members integrally supported to be capable of swinging around the shaft between a binding position in which the second teeth portion clamps and binds the sheet bundle with the first teeth portion and a standby position in which the second teeth portion is apart from the first teeth portion. The second arm member is provided over the first arm member so as to cover a part of the first arm member.