A cylinder device includes: an inner cylinder in which a functional fluid, a fluid property of which is changed due to an electric field or a magnetic field, is encapsulated; an outer cylinder provided outside the inner cylinder; an intermediate cylinder provided between the inner cylinder and the outer cylinder to serve as an electrode or a magnetic pole; a rod guide provided to close the one end side end portions of the inner cylinder and the outer cylinder; a spacer having one end located at the rod guide side and the other end located at the one end side of the intermediate cylinder, and fitted to the inner cylinder; and an elastic seal member disposed in a portion of the other end of the spacer, and configured to seal the one end side end portion of the passage between the intermediate cylinder and the inner cylinder.