concretely in order to correct blur the blur correcting lens group the rear lens group 12 is arranged to move in a direction perpendicular to the optical axis in accordance with the magnitude of a shake imposed on the viewing optical apparatus in the case where the rear lens group 12 the blur correcting lens group has a positive power the positive power of the front lens group 11 becomes weaker so that the correcting of aberrations is easier as a result the structure of an optical system can be simplified a tolerance on production can be made larger i e the requirement of tolerance can be less strict and precision thereof can be enhanced further for the purpose of comparison fig1 and 15 show the blur correcting lens group 12 respectively having a positive power and a negative power in the case where the positive blur correcting lens group 12 fig1 is provided the distance b between the blur correcting lens group 12 and the image erecting optical system p i e an optical element on the eyepiece side with respect to the blur correcting lens group 12 can be made longer compared with the case where the negative blur correcting lens group 12 fig1 is provided in other words by providing the positive blur correcting lens group 12 fig1 the overall length tl u2032 the equivalent air thickness of the overall length of the objective optical system i of the objective optical system i is made longer than the focal length fo thereof so that the distance b becomes longer compared with the case where the negative blur correcting lens group 12 is used conditions 1 to 3 are for providing.