A blade driving device includes a blade for covering an opening for an imaging device operable through motor driving and a user manual operation. A blade driving device includes a base with an opening for an imaging device, a movable member movable relative to the base in X-direction and including a slider held on the base and movable in X-direction, a blade connected to the slider, and a knob on a side of the base opposite to the slider and operable to move the blade, a motor that moves the movable member in X-direction until the blade covers or uncovers the opening in the base, and a lead screw and a driving member that transmit rotation of the motor to the slider in the movable member to move the movable member.