To solve the problems wherein, in a device for conveying paper sheets by a conveyance means, measuring simultaneously a frictional characteristic of the paper sheets, and discriminating the state of the paper sheets, if a moisture content rate of the paper sheets is changed, the frictional characteristic of the paper sheets is also changed, and thereby the state of the paper sheets cannot be discriminated accurately by a fixed discrimination value, and even a normal bill is sometimes repayed.

A contact type temperature/humidity sensor capable of responding at high speed with high accuracy is provided on an upstream part on the conveyance side of a roller pair. The moisture content rate of each paper sheet is detected instantly by being brought into contact with the paper sheet when conveying the paper sheets, and a frictional characteristic discrimination value is determined from a detected value, and compared with a measured value of a frictional force (or a friction coefficient), to thereby discriminate an abnormal bill from a normal bill.