Display control method, computer program, display control device and image display system

[Problem] To provide a display control method, computer program, display control device and image display system capable of improving operability for a user when a plurality of screens are displayed on one display device. [Solution] A work area generation unit (13) generates a plurality of areas corresponding to a plurality of display areas to be displayed upon a display screen (54) and assigns the first-mentioned plurality of areas to within one work area. A pointer position monitoring unit (15), if only a display area A (parent screen) is displayed on the display screen (54) (if PinP functioning is off), assesses whether or not a pointer position has moved from area a to area b, and outputs the assessment result to a simultaneous display instruction generation unit (17). The simultaneous display instruction generation unit (17), when the pointer position monitoring unit (15) assesses that the pointer position has moved from the area a to the area b, outputs a PinP-function-ON instruction to a display device (50).