A variable power relay optical system comprising: a variable power lens performing zooming a secondary image based on light from a primary image; and a rear group forming the secondary image based on the light passing through the variable power lens; the variable power lens consisting of, in order from the primary image side, a first group having positive power, a second group having negative power, a third group having positive power, and a fourth group having positive power, upon zooming from a high magnification end to a low magnification end, the fourth group being moved to the secondary image side, and a distance between the first group and the second group increasing, positions of the primary image and the secondary image, an entrance pupil of the variable power relay optical system, a pupil of the variable power lens, and an exit pupil of the variable power relay optical system being substantially kept constant, and the pupil of the variable power lens being disposed to the secondary image side of the last surface of the variable power lens.