A shock absorber comprising: an outer tube on which a piston rod is mounted, and in which the piston rod is reciprocable in an axial direction, the piston rod having a projecting end projecting from a distal end of the outer tube; an inner tube rotatably mounted in the outer tube, the inner tube and the outer tube collectively forming a liquid accommodating chamber to which liquid is injected, the inner tube is provided with a plurality of communication holes arranged at intervals in a circumferential direction thereof, and formed so as to penetrate through the inner tube in a radial direction thereof; and; a rotative operating part provided at the inner tube, the rotative operating part projecting from a base end of the outer tube; and a spring member disposed in a shock absorbing chamber_, the spring member applying a spring force to the piston rod in a projecting direction of the piston rod; characterized in that the shock absorber further comprises a flow-rate adjusting hole consisting of a contact surface being in contact with an outer peripheral surface of the inner tube and an eccentric surface being eccentric in the radial direction with respect to a rotation central axis of the inner tube and forming, together with an outer peripheral surface of the inner tube, a bypass channel communicated with the communication hole, the flow-rate adjusting hole provided on an inner peripheral surface of the outer tube, a communication opening degree of the bypass channel and the communication hole is configured to be changed by rotating the inner tube, a radius (Rq) of the eccentric surface (5.2) is larger than the rotation radius (Rp) of the inner tube, and an eccentric quantity (e) relative to the rotation central axis of the inner tube is set to be larger than the difference between the radius (Rq) of the eccentric surface and the rotation radius (Rp) of the inner tube, the shock absorber has: a fully-opened state having a maximum value of the communication opening degree; and a closed state having a minimum value of the communication opening degree, between the fully-opened state and the closed state, the communication opening degree is changeable depending on a rotation angle of the inner tube with respect to the outer tube in a stepless manner. an outer tube on which a piston rod is mounted, and in which the piston rod is reciprocable in an axial direction, the piston rod having a projecting end projecting from a distal end of the outer tube; an inner tube rotatably mounted in the outer tube, the inner tube and the outer tube collectively forming a liquid accommodating chamber to which liquid is injected, the inner tube is provided with a plurality of communication holes arranged at intervals in a circumferential direction thereof, and formed so as to penetrate through the inner tube in a radial direction thereof; and; a rotative operating part provided at the inner tube, the rotative operating part projecting from a base end of the outer tube; and a spring member disposed in a shock absorbing chamber_, the spring member applying a spring force to the piston rod in a projecting direction of the piston rod; characterized in that the shock absorber further comprises a flow-rate adjusting hole consisting of a contact surface being in contact with an outer peripheral surface of the inner tube and an eccentric surface being eccentric in the radial direction with respect to a rotation central axis of the inner tube and forming, together with an outer peripheral surface of the inner tube, a bypass channel communicated with the communication hole, the flow-rate adjusting hole provided on an inner peripheral surface of the outer tube, a communication opening degree of the bypass channel and the communication hole is configured to be changed by rotating the inner tube, a radius (Rq) of the eccentric surface (5.2) is larger than the rotation radius (Rp) of the inner tube, and an eccentric quantity (e) relative to the rotation central axis of the inner tube is set to be larger than the difference between the radius (Rq) of the eccentric surface and the rotation radius (Rp) of the inner tube, the shock absorber has: a fully-opened state having a maximum value of the communication opening degree; and a closed state having a minimum value of the communication opening degree, between the fully-opened state and the closed state, the communication opening degree is changeable depending on a rotation angle of the inner tube with respect to the outer tube in a stepless manner.