It is possible to provide a mobile display device which can improve usability even when the character size is increased for improving visibility. A method for controlling the mobile display device is also disclosed. A control unit (18) can set a conversion candidate of an input character displayed on a second display region (conversion candidate character display region (162)) of a display unit (16) to a first display mode (normal mode) for displaying the conversion candidate in a first character size and to a second display mode (enlarged mode) for displaying the conversion candidate in a second character size greater than the first character size while differentiating a display priority of a plurality of conversion candidates to be displayed in the second display region in the first display mode and a display priority of a plurality of conversion candidates to be displayed in the second display region in the second display mode.