To produce an optical device having a glance detector at low cost and to enable miniaturization.

Under an eyepiece lens 21, a pair of IRED 24 for eyeball illumination are provided symmetrically to the optical axis of a finder so that the intersection of central optical axes n1 and n2 of the respective IRED 24 can be almost coincident with an intersection X between an eye point E of a finder optical system and an optical axis (m) of the finder, and a pair of illuminating means can sufficiently illuminate even naked eyes or eyeballs put on glasses.