An advancing/retracting mechanism of a lens barrel, including a rotatable ring; a non-rotatable advancing/retracting guide ring positioned inside the rotatable ring including an inclined lead slot, and at least one circumferential slot which is communicatively connected with the inclined lead slot; a driven member having a follower engaged in the inclined lead slot and the circumferential slot, and further engaged in the rotation transfer groove; an optical element supported by the driven member; and a ring spring positioned inside the rotatable ring along an inner peripheral surface thereof and supported by the rotatable ring. The follower is disengaged from the follower pressing portion of the ring spring when the follower is engaged in the inclined lead slot. The follower is engaged with the follower pressing portion and resiliently deforms the follower pressing portion when the follower is engaged in the circumferential slot.