A sheet processing apparatus includes a first binding unit configured to bind a sheet bundle; a second binding unit with greater number of bindable sheets than number of bindable sheets of the first binding unit; and a number-of-sheets determining unit configured to determine whether number of to-be-bound sheets exceeds the number of bindable sheets of the first binding unit. The first binding unit moves to a binding position, and if the number-of-sheets determining unit determines that the number of to-be-bound sheets exceeds the number of bindable sheets of the first binding unit, the first binding unit moves away from the binding position. When the number-of-sheets determining unit determines that the number of to-be-bound sheets exceeds the number of bindable sheets of the first binding unit, the second binding unit moves to the binding position.