A binocular device includes two observation optical systems, an additional optical system, and a viewfinder for the additional optical system. An image-capturing unit is movable between a first image-plane position of one of the observation optical systems and an image-plane position of the additional optical system by shifting a lens-switching lever. A switch of the image-capturing unit can be turned on and off by a camera switch lever. For an observation mode using the observation optical system, the image-capturing unit is set at the image-plane position of the additional optical system. For an image-capturing mode using the observation optical system, the image-capturing unit is set at the first image-plane position such that the switch of the image-capturing unit is turned on. For image-capturing using the additional optical system, the image-capturing unit is set at the image-plane position of the additional optical system such that the switch of the image-capturing unit is turned on.