A butterfly valve that is motor-operated, comprising: a body having an inner wall defining a passage for a fluid; a shaft rotatably supported by the body; a valve element disposed in the passage in a state in which the valve element is mounted on the shaft such that the valve element turns with the shaft to adjust open and closed states or an opening degree of the passage, wherein the valve element includes a metal plate and an elastic member covering an outer surface of the plate, and has a symmetric structure with respect to an axis of the valve element; an actuator for driving the shaft to rotate when power is supplied; a shield member that is mounted on the body such that the shield member is inserted in the passage to partially block flow of the fluid through the passage, wherein the shield member includes a shield wall (120, 320) that protrudes from an inner wall of the body and has a surface having a shape following a turning trajectory of an outer edge of the valve element; and a variable opening (124, 324) constituted by a cutout formed on the shield wall (120, 320) in a turning direction of the valve element, an opening area of the variable opening (124, 324), through which flow of the fluid is permitted, varying depending on a turning angle of the valve element, wherein the valve element includes a flow rate adjusting part that is shifted along the surface of the shield wall (120, 320) to change the opening area of the variable opening (124, 324), and a seal part made of an elastic material that touches and leaves the inner wall of the body to close and open the passage, the flow rate adjusting part and the seal part being located at different positions from each other, wherein the elastic member comprises a plurality of beads (100 to 106) each having an arc shape along the outer circumferential surface of the elastic member and being formed to protrude from the outer circumferential surface, wherein first, second and third beads (100, 101, 102) are formed on one side of the valve element with respect to the axis, and fourth, fifth and sixth beads (104, 105, 106) are formed on the other side of the valve element with respect to the axis, wherein the third and fourth beads (102, 104) function as the seal part, wherein when the valve element turns in one direction, third and fourth beads (102, 104) come into contact with the inner wall to close the passage, wherein second and fifth beads (101, 105) are arranged along the outermost circumference of the valve element and function as flow rate adjusting parts that adjust a minute opening degree of the valve section. a body having an inner wall defining a passage for a fluid; a shaft rotatably supported by the body; a valve element disposed in the passage in a state in which the valve element is mounted on the shaft such that the valve element turns with the shaft to adjust open and closed states or an opening degree of the passage, wherein the valve element includes a metal plate and an elastic member covering an outer surface of the plate, and has a symmetric structure with respect to an axis of the valve element; an actuator for driving the shaft to rotate when power is supplied; a shield member that is mounted on the body such that the shield member is inserted in the passage to partially block flow of the fluid through the passage, wherein the shield member includes a shield wall (120, 320) that protrudes from an inner wall of the body and has a surface having a shape following a turning trajectory of an outer edge of the valve element; and a variable opening (124, 324) constituted by a cutout formed on the shield wall (120, 320) in a turning direction of the valve element, an opening area of the variable opening (124, 324), through which flow of the fluid is permitted, varying depending on a turning angle of the valve element, wherein the valve element includes a flow rate adjusting part that is shifted along the surface of the shield wall (120, 320) to change the opening area of the variable opening (124, 324), and a seal part made of an elastic material that touches and leaves the inner wall of the body to close and open the passage, the flow rate adjusting part and the seal part being located at different positions from each other, wherein the elastic member comprises a plurality of beads (100 to 106) each having an arc shape along the outer circumferential surface of the elastic member and being formed to protrude from the outer circumferential surface, wherein first, second and third beads (100, 101, 102) are formed on one side of the valve element with respect to the axis, and fourth, fifth and sixth beads (104, 105, 106) are formed on the other side of the valve element with respect to the axis, wherein the third and fourth beads (102, 104) function as the seal part, wherein when the valve element turns in one direction, third and fourth beads (102, 104) come into contact with the inner wall to close the passage, wherein second and fifth beads (101, 105) are arranged along the outermost circumference of the valve element and function as flow rate adjusting parts that adjust a minute opening degree of the valve section.