The lens unit (5) according to the present invention is provided in any one of a plurality of lenses, a cylindrical lens holding frame (50) that holds the plurality of lenses inside, and the plurality of lenses, The lens holding frame (50) protrudes from the stepped portion having a stepped shape along the direction of the optical axis of the lens and the inner peripheral surface of the lens holding frame (50) according to the arrangement of the lens formed with the stepped portion. And a convex portion projecting into a space formed by the inner peripheral surface and the step portion.本発明にかかるレンズユニット（５）は、複数のレンズと、複数のレンズを内部で保持する筒状のレンズ保持枠（５０）と、複数のレンズのうちのいずれかのレンズに設けられ、該レンズの光軸の方向に沿って段付き形状をなす段部と、レンズ保持枠（５０）の内周面から、段部が形成されたレンズの配置に応じて突出し、レンズ保持枠（５０）の内周面と段部とにより形成される空間に突出している凸部と、を備えた。
