An image display system includes an image display apparatus and an image signal supply apparatus which are connected to each other via an interface and displaying an image based on an image signal supplied from the image signal supply apparatus on the image display apparatus, wherein the image signal supply apparatus includes: an imaging unit taking an image of a subject; a movable holding unit holding the imaging unit and having a first state and a second state other than the first state; a state detector detecting which state of the first state and the second state the movable holding unit has; and an image signal supply apparatus controller transmitting the image acquired by the imaging unit and the detection result of the state detector via the interface, and wherein the image display apparatus includes: a state detection result acquiring unit acquiring the detection result of the state detector transmitted from the image signal supply apparatus; and an image display apparatus controller displaying a predetermined image other than the image based on the image signal transmitted from the image signal supply apparatus when it is determined that the movable holding unit has the second state on the basis of the detection result acquired by the state detection result acquiring unit, and displaying the image based on the image signal transmitted from the image signal supply apparatus when it is determined that the movable holding unit has the first state on the basis of the detection result acquired by the state detection result acquiring unit.