To immediately discontinue an abnormal medium inserting operation by detecting this abnormal insertion of a medium via a detection means in response to the fast inserting force of the medium that is put into a medium inserting port.

When a card sensor placed at the inlet position of a card inserting path detects that a card 14 is put into a card inserting port 12, a CPU drives a shutter solenoid 18 to open a shutter 13. If the inserting speed of the card 14 is higher than a normal speed, the card sensor cannot detect the card 14. Thus, a card detection switch 17 is turned on by the tip of the card 14 via a hanging plate 15 to detect the fast abnormal insertion improper for the reception of the card 14. As a result, an abnormal inserting operation of the card 14 is immediately discontinued.