In a joint mechanism having at least one joint member connected to a connectable member via a joint to be rotatable in a range between an extended position and a bent position, it is configured to have a movable cover constituting a part of a joint member cover that covers the joint member and the movable cover is moved into interior of remaining portion of the joint member cover as the joint member is rotated relative to the connectable member about the joint from the extended position to the bent position. The joint mechanism can be suitably used in fingers of a hand of a humanoid robot.