A lens device (2, 202) for an imaging device having a imaging-lens and an aperture stop device that adjusts an aperture area, the lens device (2, 202) comprising: a lens barrel that houses the imaging-lens and the aperture stop device; a first operation ring that is provided on an outer circumferential portion of the lens barrel at a desired position and is provided to be rotatable in a circumferential direction of the outer circumferential portion about an axis line of the lens barrel as a rotation axis in order to adjust the aperture area of the aperture stop device; a second operation ring that is provided in parallel with the first operation ring and provided to be rotatable in the circumferential direction of the outer circumferential portion about the axis line of the lens barrel as the rotation axis in order to adjust a transmittance of a variable light transmission filter; and a mechanism section configured to be able of switching the state that transfers rotation of the first operation ring and the second operation ring to each other in an engagement state of the first operation ring and the second operation ring, and the state that blocks from each other the rotation in a non-engagement state of the first operation ring and the second operation ring, such that the operation rings are separately operable in the blocking state, wherein a rotation direction, in which the aperture area of the aperture stop device is increased by the first operation ring, is the same as a rotation direction in which the transmittance of the variable light transmission filter is increased by the second operation ring, and wherein the mechanism section is configured to be able to convert the rotations of the first operation ring and the second operation ring into rotations in directions the same as each other or directions opposite to each other and transfer the rotations. a lens barrel that houses the imaging-lens and the aperture stop device; a first operation ring that is provided on an outer circumferential portion of the lens barrel at a desired position and is provided to be rotatable in a circumferential direction of the outer circumferential portion about an axis line of the lens barrel as a rotation axis in order to adjust the aperture area of the aperture stop device; a second operation ring that is provided in parallel with the first operation ring and provided to be rotatable in the circumferential direction of the outer circumferential portion about the axis line of the lens barrel as the rotation axis in order to adjust a transmittance of a variable light transmission filter; and a mechanism section configured to be able of switching the state that transfers rotation of the first operation ring and the second operation ring to each other in an engagement state of the first operation ring and the second operation ring, and the state that blocks from each other the rotation in a non-engagement state of the first operation ring and the second operation ring, such that the operation rings are separately operable in the blocking state, wherein a rotation direction, in which the aperture area of the aperture stop device is increased by the first operation ring, is the same as a rotation direction in which the transmittance of the variable light transmission filter is increased by the second operation ring, and wherein the mechanism section is configured to be able to convert the rotations of the first operation ring and the second operation ring into rotations in directions the same as each other or directions opposite to each other and transfer the rotations.