Abstract: An intermediate sheet storage device which comprises: controlling and checking apparatus (19) and signalling device (18) provided for the control of at least two groups of belt conveyors which embody a predetermined path provided for being followed by a sheet (4) during its handling. Particularly, the sheet (4) is forced to take a curvilinear shape along the path, the same shape taken by the groups of belt conveyors. Moreover, the storage device comprises a first diverting element (16) and a second diverting element (17), each of these is arranged to take a first position that allows the sheet (4) to follow a predetermined path as far as a dwell position (15) and a second position that diverts the sheet from its path and sends the sheet or stack of sheets to a collecting cassette (6) or to an outlet slot (7) for returning it to the user.