A lens unit (5) according to the present invention includes a plurality of lenses, a lens holding frame (50) having a tubular shape and configured to hold the plurality of lenses inside thereof, a step portion provided in any of the plurality of lenses and having a stepped shape along a direction of an optical axis of the lens, and a convex portion protruding from an inner circumferential surface of the lens holding frame (50) into a space formed by the inner circumferential surface of the lens holding frame (50) and the step portion, in accordance with a position of the lens in which the step portion is formed.
