PURPOSE: To provide a judging device for the thickness of papers, which can accurately judge thickness at all times without degrading judging accuracy even if the judging position of paper is fluctuated by providing a judging means which judges the thickness of papers based on the output of a conversion means with the use of each judging threshold value selected by a selection means.

CONSTITUTION: When a note P is carried while being put to the left side, a control section 27 detects a carrying position in the direction perpendicularly intersected with the direction by which the note P is carried, so as to store it in a first memory section 28. Next, information on thickness is taken in when the note P passes through the thickness detectors 4 and 5, so as to be temporarily stored in a second memory section 29. Information on the left end position is then computed based on information on the carrying position store in the first memory section 28. Based on the aforesaid information, judging threshold values corresponding to the thickness judging detectors 4 and 5 are selected out of a judging threshold value table housed in a third memory section 30 so as to be taken out. The judging threshold values thus taken out are compared with information on thickness temporarily stored in the second memory section 29 respectively.