To prevent a malfunction, such as a paper jam, when the state of papers stacked on a stacking unit, such as a paper discharge tray, becomes abnormal, irrespective of the cause.

A drive controlling unit 611 causes an ascending and descending unit 605 to lower the paper discharge tray 623, and then, causes raising of the paper discharge tray 623 until detection of the upper surface of the paper by an upper surface detection sensor 650. A determining unit 613 determines whether a raising time of the paper discharge tray 623 measured by a measuring unit 612 is a prescribed abnormal time. When the raising time is determined by the determining unit 613 not to be the abnormal time, the drive controlling unit 611 causes the paper discharge unit to execute the subsequent paper discharge into the paper discharge tray 623. When the raising time is determined by the determining unit 613 to be the abnormal time, the drive controlling unit causes the paper discharge unit to stop the subsequent paper discharge into the paper discharge tray 623.