To provide an optical device capable of achieving downsizing the whole device as a consequence by downsizing a driving means for carrying out focusing operation.

In the optical device which is an optical system comprising at least one lens, an image pickup element for receiving object side light passing through the lens, and an optical filter member arranged between the lens and image pickup element, having the driving means for moving the image pickup means in the direction of the optical axis, and also carrying out focusing operation of the optical system by moving the image pickup means by the driving means in the direction of the optical axis with respect to the lens, a relative distance between the optical filter member and the image pickup element is varied according to the focusing operation. Thus, the driving means for focusing operation is downsized, and the whole optical device can be downsized as a consequence.