A step actuator comprising: a first housing and a second housing; a stator wherein the stator includes a first bobbin, a second bobbin, a first yoke, and a second yoke installed between the first housing and the second housing, wherein the first yoke includes a first body section having a ring shape, a first tooth protruding from an inner peripheral surface of the first body section toward the first housing so as to be disposed between the first bobbin and a magnet, and wherein the second yoke includes a second body section having a ring shape, a second tooth protruding from an inner peripheral surface of the second body section toward the second housing so as to be disposed between the second bobbin and the magnet;a rotor including the magnet positioned radially inward from the stator, the rotor adapted to rotate and protruding from the second housing; a bearing installed at one side of the second housing so as to be coupled with the rotor; a bearing cover coupled with the one side of the second housing to restrain movement of the bearing, wherein the bearing cover supports the bearing; wherein the first housing includes a third tooth protruding toward the second housing so as to be disposed between the first bobbin and the magnet, the second housing includes a fourth tooth protruding toward the first housing so as to be disposed between the second bobbin and the magnet, characterized by a screw member coupled with the rotor and adapted to linearly move according to the rotation of the rotor; a mounting member coupled to the bearing cover and adapted to support the screw member, wherein the bearing cover includes a coupling rim having a ring shape and coupled to the one side of the second housing, a coupling pipe extending from the coupling rim, and a locking rim protruding radially inward from an end of the coupling pipe to make contact with an outer race of the bearing. a first housing and a second housing; a stator wherein the stator includes a first bobbin, a second bobbin, a first yoke, and a second yoke installed between the first housing and the second housing, wherein the first yoke includes a first body section having a ring shape, a first tooth protruding from an inner peripheral surface of the first body section toward the first housing so as to be disposed between the first bobbin and a magnet, and wherein the second yoke includes a second body section having a ring shape, a second tooth protruding from an inner peripheral surface of the second body section toward the second housing so as to be disposed between the second bobbin and the magnet;a rotor including the magnet positioned radially inward from the stator, the rotor adapted to rotate and protruding from the second housing; a bearing installed at one side of the second housing so as to be coupled with the rotor; a bearing cover coupled with the one side of the second housing to restrain movement of the bearing, wherein the bearing cover supports the bearing; wherein the first housing includes a third tooth protruding toward the second housing so as to be disposed between the first bobbin and the magnet, the second housing includes a fourth tooth protruding toward the first housing so as to be disposed between the second bobbin and the magnet, characterized by a screw member coupled with the rotor and adapted to linearly move according to the rotation of the rotor; a mounting member coupled to the bearing cover and adapted to support the screw member, wherein the bearing cover includes a coupling rim having a ring shape and coupled to the one side of the second housing, a coupling pipe extending from the coupling rim, and a locking rim protruding radially inward from an end of the coupling pipe to make contact with an outer race of the bearing.