To provide a binocular magnifier in which magnification of magnifying optical system units is changed in accordance with an operating part.

In the binocular magnifier 10, spectacle lenses 12 and 13 are mounted on a frame 11, and left and right magnifying optical system units 14 and 15 which are used to magnify an object for observation, are adhered to the center sections of the lenses. The magnifying optical system unit 14 is provided with an objective lens 14a, an eyepiece 14b and a roof-prism 14c. The objective lens 14a is integrated into an objective lens barrel 20 and the roof-prism 14c is integrated into a housing 30. The objective lens barrel 20 is provided with a screw type engaging section 20b and a screw type mounting section 31a is formed on an objective plate 31 which is located opposite to a first surface A of the roof-prism 14c. The objective plate 31 is mounted onto a side surface plate 34 by screws 35 in an attachable and detachable manner so as to clean the first surface A by detaching.