In an imaging apparatus capable of selectively performing an imaging operation in normal imaging mode and that in composite imaging mode, auto exposure control is stopped after the auto exposure control for long-time exposure image signals and short-time exposure image signals is temporarily completed in composite imaging mode and if, after the auto exposure control is stopped, a predetermined brightness change in images is detected continuously for a predetermined time or longer based on brightness values detected from the images obtained from a composite image signal, the imaging mode of the imaging apparatus is switched from the composite imaging mode to the normal imaging mode.