The invention relates to a viewing optical system for viewing an object image formed on a focusing screen, and an imaging apparatus comprising the same. An image erection optical system comprises a prism having an internal reflective surface. An eyepiece optical system comprises, in order from a screen side to an exit pupil side, a first lens component having negative refracting power wherein its exit pupil-side surface has a paraxial-radius-of-curvature absolute value smaller than that of its screen-side surface, a second lens component in a double-convex shape and a third meniscus lens component in a meniscus shape concave on an exit pupil side. The total number of lens components included in the eyepiece optical system is 3, and the following conditions (1), (2) and (3) are satisfied. 1.55