A shock absorber comprising: a cylinder in which fluid is sealed; a piston that is slidably fitted into the cylinder; a piston rod that is coupled to the piston and extends to an outside of the cylinder; and a valve mechanism that controls a flow of the fluid caused by sliding of the piston in the cylinder, wherein the valve mechanism includes: a valve body that is urged by urging means in a valve opening direction of a channel in which the fluid flows; a valve seat on which the valve body is seated to close the channel; an actuator that moves the valve body in a valve closing direction with thrust of a solenoid; and a fail-safe valve that is urged by a first elastic body in the valve closing direction of the valve body, at least a part of the fail-safe valve being seated on the valve body to close the channel and being spaced from the valve body to open the channel, when the fluid does not flow in the valve opening direction of the valve body, the fail-safe valve is urged by the first elastic body to thereby come into contact with the valve body and close the channel, characterized in that, when the fluid flows in the valve opening direction of the valve body, the fail-safe valve is spaced from the valve body by a fluid pressure to open the channel, and when the valve body moves most in the valve opening direction from the valve seat, the fail-safe valve is brought into contact with the valve body, the channel is closed, and a supporting portion of the valve body supports a part of the fail-safe valve, and, when the fluid flows in the valve opening direction of the valve body, at least a part of the fail-safe valve, which is in contact with a non-supporting portion other than the supporting portion of the valve body, is spaced from the valve body by the fluid pressure to open the channel. a cylinder in which fluid is sealed; a piston that is slidably fitted into the cylinder; a piston rod that is coupled to the piston and extends to an outside of the cylinder; and a valve mechanism that controls a flow of the fluid caused by sliding of the piston in the cylinder, wherein the valve mechanism includes: a valve body that is urged by urging means in a valve opening direction of a channel in which the fluid flows; a valve seat on which the valve body is seated to close the channel; an actuator that moves the valve body in a valve closing direction with thrust of a solenoid; and a fail-safe valve that is urged by a first elastic body in the valve closing direction of the valve body, at least a part of the fail-safe valve being seated on the valve body to close the channel and being spaced from the valve body to open the channel, a valve body that is urged by urging means in a valve opening direction of a channel in which the fluid flows; a valve seat on which the valve body is seated to close the channel; an actuator that moves the valve body in a valve closing direction with thrust of a solenoid; and a fail-safe valve that is urged by a first elastic body in the valve closing direction of the valve body, at least a part of the fail-safe valve being seated on the valve body to close the channel and being spaced from the valve body to open the channel, when the fluid does not flow in the valve opening direction of the valve body, the fail-safe valve is urged by the first elastic body to thereby come into contact with the valve body and close the channel, characterized in that, when the fluid flows in the valve opening direction of the valve body, the fail-safe valve is spaced from the valve body by a fluid pressure to open the channel, and when the valve body moves most in the valve opening direction from the valve seat, the fail-safe valve is brought into contact with the valve body, the channel is closed, and a supporting portion of the valve body supports a part of the fail-safe valve, and, when the fluid flows in the valve opening direction of the valve body, at least a part of the fail-safe valve, which is in contact with a non-supporting portion other than the supporting portion of the valve body, is spaced from the valve body by the fluid pressure to open the channel.