An electric linear actuator comprising: a cylindrical housing formed of aluminum light alloy; an electric motor mounted on the housing; a speed reduction mechanism for reducing the rotational speed of the electric motor via a motor shaft; and a ball screw mechanism for converting the rotational motion of the electric motor to an axial linear motion of a driving shaft via the speed reduction mechanism; the ball screw mechanism comprising: a nut formed with a helical screw groove on its inner circumference and supported by a pair of supporting bearings (15, 16) mounted on the housing rotationally but axially immovably, and a screw shaft integrated coaxially with the driving shaft, formed with helical screw groove on its outer circumference corresponding to helical screw groove of the nut, adapted to be inserted into the nut via a large number of balls, and supported on the housing not rotationally but axially movably; the housing being formed with receiving bores (9, 10) for receiving the screw shaft characterized in: that a cylindrical sleeve is securely press-fitted into the receiving bore of the housing, the sleeve being formed on its inner circumference at diametrically opposed positions with one pair of axially extending recessed grooves with which a guide pin mounted on the end of the screw shaft being engaged, and that an annular groove is formed near an opening of the receiving bore of the housing and the sleeve is held in the receiving bore not to come out therefrom with being pressed by a stopper ring snapped in the annular groove. a cylindrical housing formed of aluminum light alloy; an electric motor mounted on the housing; a speed reduction mechanism for reducing the rotational speed of the electric motor via a motor shaft; and a ball screw mechanism for converting the rotational motion of the electric motor to an axial linear motion of a driving shaft via the speed reduction mechanism; the ball screw mechanism comprising: a nut formed with a helical screw groove on its inner circumference and supported by a pair of supporting bearings (15, 16) mounted on the housing rotationally but axially immovably, and a screw shaft integrated coaxially with the driving shaft, formed with helical screw groove on its outer circumference corresponding to helical screw groove of the nut, adapted to be inserted into the nut via a large number of balls, and supported on the housing not rotationally but axially movably; a nut formed with a helical screw groove on its inner circumference and supported by a pair of supporting bearings (15, 16) mounted on the housing rotationally but axially immovably, and a screw shaft integrated coaxially with the driving shaft, formed with helical screw groove on its outer circumference corresponding to helical screw groove of the nut, adapted to be inserted into the nut via a large number of balls, and supported on the housing not rotationally but axially movably; the housing being formed with receiving bores (9, 10) for receiving the screw shaft characterized in: that a cylindrical sleeve is securely press-fitted into the receiving bore of the housing, the sleeve being formed on its inner circumference at diametrically opposed positions with one pair of axially extending recessed grooves with which a guide pin mounted on the end of the screw shaft being engaged, and that an annular groove is formed near an opening of the receiving bore of the housing and the sleeve is held in the receiving bore not to come out therefrom with being pressed by a stopper ring snapped in the annular groove. that a cylindrical sleeve is securely press-fitted into the receiving bore of the housing, the sleeve being formed on its inner circumference at diametrically opposed positions with one pair of axially extending recessed grooves with which a guide pin mounted on the end of the screw shaft being engaged, and that an annular groove is formed near an opening of the receiving bore of the housing and the sleeve is held in the receiving bore not to come out therefrom with being pressed by a stopper ring snapped in the annular groove.