To provide an image shake correcting optical apparatus using a small, lightweight engaging mechanism for the correction lens holder engaging mechanism. A ring-shaped engaging member 16 formed of shape memory alloy and having three engaging arms on its inside is located outside a lens holder 11 for a correction lens L3, and the engaging contacts 16b at the tips of the engaging arms 16a are pushed toward the center of the ring-shaped engaging member by means of coil springs 17. The engaging member 16 formed of shape memory alloy has a prescribed memorized shape so that the arms 16a will assume a retracted position, and where no heat is applied, the engaging contacts 16b of the engaging arms press onto the lens holder 11 for the correction lens L3 from the outside due to the spring force of the coil springs 17, and engages with and maintains in place the lens holder 11. Where heat is applied, the engaging arms 16a retract, whereupon the engagement of the lens holder 11 is terminated.