A stereoscopic image viewing device to be attached for stereoscopic image viewing to eyeglasses; which includes: a pair of light shutters for right and left eyes; a driver circuit for the light shutters; a power source unit for driving the light shutters; a bridge for supporting the light shutters at their inside edges; a binding portion for removably binding the stereoscopic image viewing device to the eyeglasses; and a support for supporting the driver circuit and the power source unit. The power source unit includes a secondary battery. The binding portion and the support are integrally formed with the bridge. The stereoscopic image viewing device has a center of gravity positioned in the bridge.