A rotation driving device comprises a first fixed member having an aperture, a second fixed member having an aperture, the second fixed member being fixed with respect to the first fixed member, a ring-like rotary member, the rotary member being fitted in the first fixed member at an outer diameter portion of the rotary member and being fitted in the second fixed member at a diameter portion of the rotary member having a diameter smaller than that of the outer diameter portion, and a moving member arranged to advance and retreat in a radial direction of the rotary member in accordance with a rotation of the rotary member, wherein, where an amount of fitting play between the second fixed member and the rotary member is denoted by X and an amount of fitting play between the first fixed member and the rotary member is denoted by Y, the rotation driving device satisfies the following condition:X