A water-resistant structure of a lens barrel includes a sealing member that seals an annular gap between inner and outer annular members, wherein the sealing member is positioned in a vicinity of an open end of the outer annular member and is fixed to one of the inner and outer annular members to be slidable on the other of the inner and outer annular members, and a drain groove formed on the inner annular member and positioned alongside the sealing member at a position closer to the open end of the outer annular member than the sealing member. Furthermore, a frictional resistance of a first sealing member produced between a secondary annular member and a manually-rotatable annular members is greater than a frictional resistance of the second sealing member that urges one of two of the manually-rotatable annular members to follow a rotation of the other thereof when rotated.