Disclosed herein is a speed controller of a type wherein a check valve flexed depending on the flow direction of a pressurized fluid can be seated on a seat portion of a main body thereof and separated therefrom. The main body has first and second connecting portions capable of communicating with a pressurized-fluid flow channel defined in a pressurized fluid device. A needle valve mechanism is provided in continuation with a passage defined in the main body. When the pressurized fluid is introduced from the first connecting portion, the check valve is tightly fitted on a seat portion formed in the main body so as to close the passage and the second connecting portion. On the other hand, when the pressurized fluid is introduced from the second connecting portion, the check valve is separated from the seat portion so as to close the first and second connecting portions and discharge the pressurized fluid introduced from the second connecting portion into the needle valve mechanism via the passage. Therefore, water vapor can be prevented from adhering to the pressurized-fluid flow channel for allowing an electromagnetic valve to communicate with a cylinder. The response time of the cylinder can be shortened as a whole and the degree of freedom of arrangement of devices can be improved.