To provide a blade driving device and an optical instrument, in which blade displacement is restricted.

A blade driving device according to the invention comprises: a substrate with an aperture; first and second blades which is capable of swinging around first and second fulcrums, respectively, and bring at least part of the aperture into a closed state in which the part is closed or a retreated state in which the part is retreated; and a drive ring which has first and second drive pins engaged with the first and second blades respectively and is capable of rotating around the aperture. The positions of the first and second fulcrums are symmetrical around the center of the aperture. The positions of the first and second drive pins in the retreated state are symmetrical around the center of the aperture. The positions of the gravity centers of the first and second blades in the retreated state are symmetrical around the center of the aperture.