PURPOSE: To arrange the above air flowrate adjusting mechanisms to be concentrated at one position by providing a connection tightening section at least at one end of a barrel section, regarding an air flowrate adjusting mechanism having a barrel section, an air tube connecting section and a flowrate adjusting handle.

CONSTITUTION: An air flowrate adjusting mechanism (speed controller) fitted to the air cylinder drive means of each type of devices has an air tube connecting section 2 on a barrel section 1. One end of the barrel section 1 is fitted with a flowrate adjusting handle 3 and the other end is fitted with a connection tightening section 4. This tightening section 4 comprises a lock nut 41 and a tightening nut 43 screwed to the threaded section 42 of the barrel section 1. The threaded section 42 is inserted, for example, in a mounting hole drilled through a panel 5, and the nut 4 is kept in contact with one side of the panel 5. Then, the tightening nut 43 is screwed from the other side of the panel 5. The air flowrate adjusting mechanism is thereby mounted, with the panel 5 clamped under pressure between both nuts 41 and 42.