To display karaoke lyric characters smaller than a display size set as a default without requiring troublesome operations when displaying externally input image data stored in an external storage medium as a background image.

A karaoke lyric character size control system includes connection confirmation means 39 for confirming a connection of an external storage medium 27, background image selection means 40 for selecting background image data set as a default for each music piece as a background image when the connection of the external storage medium 27 is not confirmed, and selecting externally input image data stored in the external storage medium 27 as a background image when the connection of the external storage medium 27 is confirmed, and lyric character size selection means 42 for selecting a display size set as a default when the background data is selected, and selecting a display size smaller than the display size set as a default when the externally input image data is selected.