A slight-vibration-suppressing mechanism is attached to a piston rod 6 of
an air pressure cylinder that stops the piston at a target position by
means of a positioning control. The slight-vibration-suppressing
mechanism includes a friction member formed of a pair of sealing members
being in contact with the piston rod, and an air cell of compressed air
fed to a periphery of the piston rod is formed by means of the friction
member. An air flow path to feed and discharge the compressed air to the
aforementioned air cell is formed, in which the compressed air generates
a sliding friction, which suppresses slight vibration, via the friction
member between the piston rod and the aforementioned friction member.