1. An apparatus comprising one or more processors carrying out functions of a first obtaining unit, a second obtaining unit, a generation unit, a synthesizing unit, a determination unit, and a display control unit; the first obtaining unit obtaining a physical space image obtained by sensing a physical space by an image sensing device; the second obtaining unit obtaining a position and orientation of the image sensing device; the generation unit generating a virtual object based on the position and orientation obtained by the second obtaining unit; the synthesizing unit generating a synthesized image by synthesizing the physical space image with the virtual object; the determination unit determining whether an error region exists in the synthesized image; and the display control unit causing a display device to display the synthesized image in a case where the determination unit does not determine that the error region exists in the synthesized image, and to cause the display device to display the physical space image in a case where the determination unit does determine that the error region exists in the synthesized image.