The present invention provides a novel image output apparatus that includes an operation processing unit that processes an operation request from a user, a projecting unit that projects a display image from a video providing apparatus and UIs from the image projector, a determining unit that determines whether or not it is necessary to switch a source of a video signal by using a current input type and a source of a video signal with reference to a data table that associates an input type that indicates a type of a port from which an image to be projected is acquired with a source of a video signal that forms an image to be projected, and a controller that switches a source of a video signal and executes a process indicated by an operation request from a user if it is necessary to switch the source of a video signal.