The lens unit includes a jointed lens having a first optical member, a second optical member disposed on an optical axis of the first optical member, and a jointing member having a light transmissive property and disposed between the first optical member and the second optical member, and an adjustment mechanism holding the first optical member and the second optical member and adjusting a distance between the first optical member and the second optical member along an optical axis direction. The jointing member adheres to the first optical member and the second optical member in a deformable manner. The adjustment mechanism adjusts the distance to change the thickness of the jointing member along the optical axis direction.