1. A composite image creating apparatus that combines a first video and a second video photographed after the first video so as to create a composite image, the composite image creating apparatus comprising: a control unit including a central processing unit executing a control program, comprising: an image determining unit that determines a specific subject in the first video; a boundary setting unit that sets a boundary that divides a screen of the first video into a specific range and a non-specific range, the specific range including the specific subject, the non-specific range not including the specific subject; a display control unit that displays the boundary together with a live-view image of the second video when the second video is photographed; and a combining unit that combines an image within the specific range in the first video with an image within a range in the second video that corresponds to the non-specific range so as to create a composite image, wherein the boundary setting unit moves a position of the boundary according to a change in the specific subject, and the display control unit announces beforehand the position of the boundary to be moved in a case in which the set boundary is displayed in the live-view image of the second video.