A damper apparatus comprising: a damper body having a receiving hole formed therein; a piston movably disposed in the receiving hole and dividing an inner space of the receiving hole into a first chamber and a second chamber; fluid filled in the first chamber and the second chamber; a communication passage that communicates the first chamber with the second chamber and allows the fluid to flow in the communication passage substantially without resistance; a valve mechanism that opens the communication passage when the piston is moved in a direction from the first chamber to the second chamber and closes the communication passage when the piston is moved in a direction from the second chamber to the first chamber; a resistance passage that communicates the first chamber with the second chamber and provides the fluid flowing in the resistance passage with a predetermined amount of resistance; a fitting recess formed in an outer peripheral surface of the piston and extending annularly in a circumferential direction; and a seal member made of an elastic material and having an annular configuration, the seal member received in the fitting recess; wherein: a width of the fitting recess is sized to be greater than a width of the seal member in a moving direction of the piston so that the seal member can be moved inside the fitting recess in the moving direction of the piston; an outer peripheral portion of the seal member is press-contacted with an inner peripheral surface of the receiving hole by an elasticity of the seal member at least when the seal member is positioned in an end portion of the fitting recess in the second chamber side; and wherein a friction resistance generated between the outer peripheral portion of the seal member and the inner peripheral surface of the receiving hole is greater than a friction resistance generated between an inner peripheral portion of the seal member and a bottom surface of the fitting recess, characterized in that: the fitting recess and the seal member are disposed separately from the valve mechanism. a damper body having a receiving hole formed therein; a piston movably disposed in the receiving hole and dividing an inner space of the receiving hole into a first chamber and a second chamber; fluid filled in the first chamber and the second chamber; a communication passage that communicates the first chamber with the second chamber and allows the fluid to flow in the communication passage substantially without resistance; a valve mechanism that opens the communication passage when the piston is moved in a direction from the first chamber to the second chamber and closes the communication passage when the piston is moved in a direction from the second chamber to the first chamber; a resistance passage that communicates the first chamber with the second chamber and provides the fluid flowing in the resistance passage with a predetermined amount of resistance; a fitting recess formed in an outer peripheral surface of the piston and extending annularly in a circumferential direction; and a seal member made of an elastic material and having an annular configuration, the seal member received in the fitting recess; wherein: a width of the fitting recess is sized to be greater than a width of the seal member in a moving direction of the piston so that the seal member can be moved inside the fitting recess in the moving direction of the piston; an outer peripheral portion of the seal member is press-contacted with an inner peripheral surface of the receiving hole by an elasticity of the seal member at least when the seal member is positioned in an end portion of the fitting recess in the second chamber side; and wherein a friction resistance generated between the outer peripheral portion of the seal member and the inner peripheral surface of the receiving hole is greater than a friction resistance generated between an inner peripheral portion of the seal member and a bottom surface of the fitting recess, characterized in that: the fitting recess and the seal member are disposed separately from the valve mechanism. a width of the fitting recess is sized to be greater than a width of the seal member in a moving direction of the piston so that the seal member can be moved inside the fitting recess in the moving direction of the piston; an outer peripheral portion of the seal member is press-contacted with an inner peripheral surface of the receiving hole by an elasticity of the seal member at least when the seal member is positioned in an end portion of the fitting recess in the second chamber side; and wherein a friction resistance generated between the outer peripheral portion of the seal member and the inner peripheral surface of the receiving hole is greater than a friction resistance generated between an inner peripheral portion of the seal member and a bottom surface of the fitting recess, characterized in that: the fitting recess and the seal member are disposed separately from the valve mechanism.