A lens barrier opening/closing device of a movable lens barrel includes a barrier blade which is driven to open and close a photographic aperture; a barrier drive ring driven to rotate about an optical axis; a first biasing device which biases the barrier drive ring in a rotational direction; a rotational barrel which rotates about the optical axis; a receiving surface formed on the barrier drive ring to extend parallel to the optical axis; and a transmission surface, formed on the rotational barrel, extending parallel to the optical axis. The receiving surface and the transmission surface are engaged with each other to rotate the barrier drive ring together with the rotational barrel about the optical axis in a direction against a biasing force of the first biasing device when the movable lens barrel moves from either the photographing position to the accommodation position or vise versa.