PURPOSE: To properly detect a burr occurring spot in a card conveyor mechanism.

CONSTITUTION: A detecting card is made up of stacking a thermosensitive layer 14 and a protecting layer 16 on a card base material 12. This thermosensitive layer 14 is a white color layer consisting of a mixture of a vinyl hloride - vinyl acetate copolymer and a fatty derivative. When the detecting card is fed to a conveor system, the part brought into contact with a burr occurring spot of the thermosensitive layer 14 is varied into transparency by dint of pressure, so that any burr in the conveyor system is easily detectable. Since the thermositive layer 14 is reversibly varied into a white state by heating, the card is reusuable for burr detection.