A lens barrier device includes: a plurality of barrier blades disposed in an oscillatible manner in front of an imaging lens positioned in closest proximity to a subject side in an imaging optical system; and an oscillating mechanism that allows the plurality of barrier blades to oscillate so as to form a fully closed state in which an optical path of the imaging optical system is fully closed and a fully opened state in which the optical path is fully opened by the barrier blades. The oscillating mechanism includes a drive ring that is provided in an inversely rotatable manner within a predetermined angular range about an optical axis of the imaging optical system and allows the plurality of barrier blades to oscillate back and forth to form the fully closed state and the fully opened state by rotating forward and backward.