A card reader includes a card locking mechanism locking a card medium in an immovable holding position when the card medium inserted from a card insertion port provided in a front section of a card reader body stops because of abnormal stopping, thus preventing wrongful removal of the card medium by withdrawal. The card locking mechanism includes a spindle able to rotate via a spindle pin at one end inside the card reader body at the card insertion port, and a stopper configuration enabling direct contact with a surface of the card medium provided along a periphery at another end. A rotation radius includes a distance from the spindle pin to the stopper configuration being gradually increased from one end of the stopper configuration to another end to increase locking force by contact with the card medium.