Heat radiation base body 23 that is adjacent to electric motor unit EM and extends in direction of rotation shaft 50 of electric motor is provided close to rotation shaft 50 of electric motor. Board 24 of one electronic control unit of redundant system is fixed to heat radiation base body along direction in which heat radiation base body 23 extends with thermal conduction to heat radiation base body 23 allowed. Board 26 of the other electronic control unit of redundant system is fixed to heat radiation base body so as to face to board 24 of one electronic control unit of redundant system, with thermal conduction to heat radiation base body 23 allowed. Size reduction of electric drive device in radial direction can be achieved. Since heat radiates to housing of electric motor unit through heat radiation base body, heat from board can radiate efficiently to the outside.