An image compositing apparatus that superimposes an overlay image signal on an area of chromakey color (8, 9) on a base image signal and outputs a composite image signal to be displayed as a composite image, the image compositing apparatus comprising: a storage unit that stores the position and size of an area (8, 9) in which said overlay image signal is displayed in the composite image; an image position and size change unit that changes the position and size of said overlay image signal in accordance with the information of said storage unit; a base image presence or absence decision unit that decides the presence or absence of said base image signal; and a chromakey decision unit that decides a chromakey color portion of said base image signal, wherein in a case where said base image presence or absence decision unit decides the presence of the base image signal and said chromakey decision unit decides that the portion of the base image signal is the chromakey color portion, the image compositing apparatus outputs a corresponding portion of said overlay image signal having the position and size changed by said image position and size change unit as the composite image signal, in a case where said base image presence or absence decision unit decides the presence of the base image signal and said chromakey decision unit decides that the portion of the base image signal is not the chromakey color portion, said image compositing apparatus outputs the portion of the base image signal as the composite image signal, and in a case where said base image presence or absence decision unit decides the absence of the base image signal, said image compositing apparatus outputs said overlay image signal having the position and size changed by said image position and size change unit as the composite image signal. a storage unit that stores the position and size of an area (8, 9) in which said overlay image signal is displayed in the composite image; an image position and size change unit that changes the position and size of said overlay image signal in accordance with the information of said storage unit; a base image presence or absence decision unit that decides the presence or absence of said base image signal; and a chromakey decision unit that decides a chromakey color portion of said base image signal, wherein in a case where said base image presence or absence decision unit decides the presence of the base image signal and said chromakey decision unit decides that the portion of the base image signal is the chromakey color portion, the image compositing apparatus outputs a corresponding portion of said overlay image signal having the position and size changed by said image position and size change unit as the composite image signal, in a case where said base image presence or absence decision unit decides the presence of the base image signal and said chromakey decision unit decides that the portion of the base image signal is not the chromakey color portion, said image compositing apparatus outputs the portion of the base image signal as the composite image signal, and in a case where said base image presence or absence decision unit decides the absence of the base image signal, said image compositing apparatus outputs said overlay image signal having the position and size changed by said image position and size change unit as the composite image signal.