An image signal output apparatus includes: a stereoscopic image generation unit that is provided with a first image signal that represents a first image and a second image signal that represents a second image with a parallax relative to the first image and that generates a stereoscopic image signal, wherein the first image is provided from a first image acquisition unit that picks up an image of a subject, and the second image is provided from a second image acquisition unit a two-dimensional image signal generation unit that generates a two-dimensional image signal based on the first image signal or the second image signal and a switching unit that can switch, for each of a plurality of output units, which image signal of the stereoscopic image signal and the two-dimensional image signal is supplied to which of the plurality of output units.
