A belt slippage correcting device includes: a belt moving part that moves a belt in a width direction of the belt; a slippage detector that detects a slippage of the belt in the width direction; a hardware processor that controls a movement of the belt caused by the belt moving part based on the slippage of the belt detected by the slippage detector; and an acquisitor that acquires paper sheet conveying property, wherein the hardware processor controls an amount of movement of the belt caused by the belt moving part based on the paper sheet conveying property acquired by the acquisitor.