To provide an operating device for a valve, having a locking mechanism capable of surely and automatically locking the valve at an intermediate opening.

In a locking device 90, a pin case 92 mounted on a lower case 49, a locking pin 93 mounted inside of the pin case 92 and coming in and out in the radial direction of an output shaft carrier 58 over a locking position to be engaged with a lock hole 94 formed on an outer peripheral face of an output shaft carrier 58 and a unlocking position to be separated from the lock hole 94, a spring 96 for pressing the lock pin 93 toward the locking position, and a release pin 97 for pressing back the lock pin 93 to the unlocking position against the pressing force by the spring, are mounted rotatably around a shaft center of an operation shaft 98.