An electro-hydraulic servomotor includes: an electric motor (41) which rotates a drive shaft (51) in response to an inputted signal; a hydraulic motor (60) which rotates an output shaft (61) using hydraulic pressure of operation oil; a first geared shaft (53) rotatable along with the output shaft (61); a second geared shaft (52) threadingly engaged with the drive shaft (51) and meshed with the first geared shaft (53); and a spool (71) axially movable along with the second geared shaft (52) depending on a rotational difference between the drive shaft (51) and the first geared shaft (53), to control supply and discharge of the operation oil to and from the hydraulic motor (60).