A servo regulator includes servo piston, a first pressure chamber and a second pressure chamber, a spool, a biasing member provided on an outer periphery of the spool and configured to bias the spool, a first support portion configured to support one end portion of the biasing member when the spool is moved to a first direction where the pressure in the first pressure chamber is raised, and a second support portion configured to support other end portion of the biasing member when the spool is moved to a second direction where the pressure in the second pressure chamber is raised, wherein at least one of the first support portion and the second support portion is detachably provided on the spool.