In accordance with an embodiment, a sheet post processing apparatus comprises a processing tray, a gluing section and a control section. Sheets are placed one by one in the processing tray. The gluing section enables glue to be adhered to the glue binding margin part of the sheets already placed in the processing tray. The control section includes a glue supply mode for supplying glue parts in such a manner that a glue part, which is different from a waiting glue part waiting for a next gluing when the previous glue binding is ended, is supplied to a glue adhering section of a first sheet for gluing with a second sheet through the gluing section.