Pneumatic servo valves are key components in pneumatic servo systems. In multi-degree-of-freedom systems such as robot systems, a lot of servo valves are installed. Nozzle flapper-type servo valves are not suitable for these systems because they release air all the time, so that air consumption is too large. Spool-type servo valves currently used allow leakage of air from a sliding portion of a spool. Therefore, in robot systems, vibration and noise of compressors are big problems. Reducing leakage of servo valves can solve these problems and save energy. In this study, we develop a 4-port pinch-type pneumatic servo valve controlling flow by pinching air tubes, aiming at a leak-less servo valve. Almost all existing pinch-type valves are 2 or 3 port and proportional valves, aiming to control flow of slurry and medicine. There are no 4-port pinch-type servo valves. Experimental results showed that the leakage was lower than 1.7% of the rated flow rate and dynamic characteristics was approximately 30 Hz. We conducted position control experiments of a pneumatic cylinder using the prototype valve and showed the effectiveness.