A lens unit includes a guided portion that includes a first bearing portion and a second bearing portion disposed to be spaced apart from each other in a direction X and is slidably supported by a guide shaft, and a lens holding member. The lens unit includes a first tilt-preventing member having a linear expansion coefficient lower than a linear expansion coefficient of the lens holding member. The first tilt-preventing member is fixed to a region of the guided portion positioned between the first bearing portion and second bearing portion.