A post-processing apparatus according to an embodiment includes an adhesive binding unit that binds a plurality of sheets into a bundle. A controller sets an allowable binding number X of sheets capable of being subject to binding at one time in the adhesive binding apparatus. The controller sets a predetermined remaining number N of sheets. The controller receives a number A of the sheets instructed to be bound in the adhesive binding unit. The controller calculates a remaining number n of sheets, where n=A-X. The controller determines whether n>N or n‰¤N. The adhesive binding unit binds the A number of the sheets into a single bundle when it is determined that n