A damper device is configured so that a piston moves in a cylinder. A seal ring member is provided to the outer periphery of the piston to device the inside of the cylinder into a first chamber and a second chamber. A transmission member is connected to the piston and can transmit external force to the piston. A cutout section is formed with a predetermined circumferential width in a first stopper surface. A communication section has an opening in an annular outer peripheral section located closer to the second chamber than the cutout section. When the seal ring member is pressed toward the first stopper surface, the seal ring member is deformed so as to partially enter the cutout section.