A medium is transferred and loaded to a media tray provided with a media processing unit which is operable to perform information processing on the medium, by using a transfer arm of a media transfer mechanism. A distance from a surface of the medium loaded on the media tray to a reference position of the transfer arm is acquired. A difference between the acquired distance and a predetermined distance from a reference surface of the media tray to the reference position of the transfer arm is calculated. It is determined that a double transfer of the medium to the media tray occurs when the calculated difference is larger than a predetermined threshold value.