1. An information device for displaying a window capable of changing its display position and its display size on a screen, the information device comprising: a controller for controlling the display position and the display size of a window; a semi-maximization instruction receiving part for receiving instructions for semi-maximizing the window; a semi-maximization region setting part for setting a plurality of display regions in which the window can be semi-maximized; and a display region determination part for determining a display region in which the window is semi-maximized, from the plurality of display regions, wherein when the semi-maximization instruction receiving part receives the instructions for semi-maximizing the window, the controller allows the window to be displayed in an entire area of the display region determined by the display region determination part from the plurality of display regions.