Thrust measurement experiment was carried out using a four-cylinder pulse detonation rocket engine (PDRE) with a rotary valve. The PDRE uses three types of gases, oxidizer, fuel, and purge gas to generate detonation wave intermittently and produces thrust. We used a rotary valve attached coaxially to a motor for supplying these three gases intermittently. The mechanism of the rotary valve is very simple. It is built up with a top cover, a rotating disk, and a casing, and has advantage to enable high mass flow rate and high frequency operation. The oxidizer was N2O, the fuel was ethylene, and the purge gas was He. In the operation time for 1000 msec with C2H4-N2O propellant, we achieved time-averaged thrust of 258.5 N and specific impulse of 138.7 sec.