Abstract: It is an object to provide a servo valve that can be manufactured at low cost by simplifying adjustment of the relative position between a nozzle and a flapper and simplifying the configuration of a valve-element driving circuit. Provided is a servo valve (1) including a spool (5) mounted so as to be movable back and forth; a first chamber (7) and a second chamber (9) that mutually push the spool (5) in opposite directions by means of fluid pressure; and a spool driving circuit (3) that supplies oil to the first chamber (7) and the second chamber (9) and that adjusts the pressure of supplied oil to move the spool (5) back and forth, wherein the spool driving circuit (3) maintains the fluid pressure of the first chamber (7) at a substantially constant level and includes, at an oil outlet of the second chamber (9), a nozzle flapper mechanism (27) that adjusts the fluid pressure of the second chamber (9).