1. An image display method, comprising: the memory step of memorizing plural window patterns described in a style designation language; the first selection step of selecting one window pattern from a plurality of window patterns including a first window pattern which displays at least one video obtained from at least one selected image sensing device, a second window pattern which displays a first map display indicating positions of at least one image sensing device existing in a first area and displays the at least one video obtained from the selected at least one image sensing device, a third window pattern which displays a second map display indicating positions of the at least one image sensing device existing in a second area wider than the first area and displays the at least one video obtained from the selected at least one image sensing device; the second selection step of selecting at least one image sensing device for obtaining a video to be displayed in an image display window; the window configuration step of presenting inquires, wherein at least one of the presented inquiries relates to the selected at least one image sensing device, and outputting window configuration information; the window generation step of generating the image display window by synthesizing the at least one video which is obtained from the image sensing device selected in the second selection step and a window pattern, selected in the first selection step, which is described in a style designation language in accordance with the window configuration information, the third selection step of, in a case where the image display window generated in the window generation step includes one of the first and second map displays, selecting the first or second area to be expressed in the other of the first and second map displays in response to an instruction for changing the image display window; and the changing step of changing the image display window, generated in the window generation step, so as to include the first or second map display expressing the first or second area selected in the third selection step.