To provide a lens barrel capable of preventing entrance of dust, while enabling highly accurate alignment.

A lens barrel 10 includes a first lens holding member (30) holding a first lens group (11), a second lens holding member (40) holding a second lens group (12), and an adjustment mechanism 50 capable of adjusting the position of the first lens holding member with respect to the second lens holding member. The first surface (40c) of the second lens holding member includes at least three positioning parts 41 being in contact with the first lens holding member in a direction of a photographic optical axis OA in a position surrounding the second lens group and a sheet member 25 attached to the first surface over a whole circumference surrounding the three positioning parts, when viewed on a plane orthogonal to the photographic optical axis OA. The sheet member 25 is pressed against the first lens holding member in the direction of the photographic optical axis OA over a whole circumference surrounding the first lens group, between the adjustment mechanism and the first surface, when viewed in the direction of the photographic optical axis OA.