A lens barrier device is provided which includes an adaptor body capable of being removably attached on a taking lens frame, a lens barrier member capale of movement between a closed position covering a taking lens and an open position withdrawn from the front of the taking lens, and an engagement member capable of engagement with a filter screwthread of the lens frame. If the lens barrier member in the open position is rotated excessively by wrong manual operation, the edge of the lens barrier member presses on the engagement member, releasing the engagement with the filter screwthread and so separating the adaptor body from the lens frame, thereby protecting the lens barrier device.