A card reader for use with a card having magnetic data recorded thereon may include a magnetic head for carrying out at least one of reading the magnetic data recorded in the card and recording the magnetic data into the card; a card insertion part where an insertion slot for inserting the card is formed; a metal sensor structured to detect a foreign object, which contains a metallic material, having been installed around the card insertion part; and a control unit. The control unit may be structured to calculate the amount of change in an output value of the metal sensor, whenever a predetermined reference time period has passed, and judge that the foreign object has been installed around the card insertion part if the amount of change exceeds a predetermined reference value.