Provided are a lens barrel and an imaging device, with which it is possible to lock an optical member of which the movement in an optical axis direction is made free in a case where there is no electrification, particularly to hold the optical member in a locked state without use of electric power. A movable frame that holds a focus lens is driven in the optical axis direction by a linear motor. In a case where the movable frame is to be locked with the linear motor being not electrified, the movable frame (engagement portion) is caused to abut onto a restriction portion at an end portion of the movable range of the movable frame and a locking ring is caused to rotationally move to a locking position by an electric actuator. Accordingly, the movable frame is fixed by the restriction portion and a locking portion of the locking ring to become unable to move. The electric actuator includes a worm gear as a power transmission mechanism and it is possible to hold the locking ring at the locking position by means of an irreversible rotation function of the worm gear.