This cylinder device of the present aspect includes: a cylinder having a bottomed tubular shape; a seal member provided at an opening of the cylinder; and a piston rod that is provided to protrude from the opening of the cylinder and slides with respect to the seal member. A sliding surface of the piston rod has a chrome-plated layer. In the sliding surface, as characteristic evaluation parameters of a plateau structure surface described in JIS B 0671-2 and ISO 13565-2, a reduced valley depth Rvk is 0.06 μm or more and less than a plating thickness, a reduced peak height Rpk is 0 μm or more and 0.04 μm or less, and a core roughness depth Rk is 0.08 μm or more and 0.16 μm or less.