The object of the present invention is to provide an anti-vibration optical system, a telephoto optical system, a binocle (binoculars), and an anti-vibration unit that are capable of appropriate distant observation even in a case where the number of reflective members is reduced.In a telephoto optical system, an anti-vibration optical system, which is provided with a first reflective member and a second reflective member, is disposed between an objective optical system and an ocular optical system. The anti-vibration optical system corrects image blurring in a first direction (pitch direction) by rotating the first reflective member around a first rotary shaft, and corrects image blurring in a second direction (yaw direction), which is orthogonal to the first direction, by rotating the first reflective member and the second reflective member around a second optical axis.