Disclosed is an shape-forming shutter apparatus including a plurality of shutter pieces, each having an shaping surface and a sliding surface, which are arranged in a circle with the shaping surface of each shutter piece being slidably in sliding contact with the sliding surface of the neighboring separate shutter piece, and the shape-forming shutter apparatus being capable of dilating and contracting an opening part surrounded by the shaping surfaces respectively of the plurality of shutter pieces. The shape-forming shutter apparatus includes pressure contact biasing means for always keeping the shaping surface of each shutter piece and the sliding surface of the neighboring shutter piece slidably in pressure contact with each other. The pressure contact biasing means is a ring-shaped elastic member for biasing the shutter pieces equally in such a direction to close the opening part. The elastic member is stretchingly wound around the shutter pieces in an end of each shutter piece, which end is separate away from the other end thereof where the shaping surface of the shutter piece and the sliding surface of the neighboring shutter piece intersect each other.