At least one exemplary embodiment is directed to a viewfinder optical system which includes a first mirror having a roof shape configured to reflect light from an object image formed by a photographic lens towards the object image, a second mirror configured to reflect light reflected from the first mirror towards an observation side, and an eyepiece lens configured to receive light reflected from the second mirror. The second mirror includes a rotationally asymmetrical surface. The eyepiece lens includes at least one rotationally asymmetrical surface. The eyepiece lens includes a plurality of lenses, among which a lens closest to the second mirror includes a rotationally asymmetrical surface.