A screen has four main regions located in a cross direction and respectively assigned to four operation images. The screen has an outer periphery region around a center region. The outer periphery region includes an unfilled outermost circumference region, a boundary region, which is between operation images adjacent to each other, and a remaining region, in which the four operation images are paved. At least one of the four operation images is located over a corresponding one main region and an adjacent region, which is adjacent to the corresponding one main region in a circumferential direction around the center region. Each of the four operation images has an image region including a largest rectangle region surrounded by sides being in parallel with sides of the screen. The largest rectangle region has an area greater than 50% of a total area of the image region.