There is provided a damper device including: a cylinder; a piston; and a seal ring. The piston includes: a column portion wound around the seal ring; and a first restricting portion and a second restricting portion that are configured to restrict movement of the seal ring in a axial direction. The column portion has a protruding portion protruding outward in a radial direction. The first restricting portion has a cutout portion. The seal ring is capable of taking a deformed state where the seal ring is deformed so as to partially enter the cutout portion by movement of the piston. In a case where the seal ring is in the deformed state, and in a normal state where the seal ring does not enter the cutout portion, the seal ring is pressed against an inner peripheral surface of the cylinder by the protruding portion.