A bucket vibration damping structure comprising: a variable contact-type vibration damping means disposed on a plurality of bucket blades (20, 30) mounted on an outer peripheral surface of a rotor disk and performing variable contact according to rotational speed of a rotor for damping vibration, wherein the variable contact-type vibration damping means comprises: a first damping member disposed on one blade of the plurality of bucket blades (20, 30); and a second damping member disposed on another blade of the plurality of bucket blades (20, 30) at a position corresponding to the first damping member on the one blade; characterized in that the first damping member comprises a first tangential portion and a second tangential portion and the second damping member comprises a first facing portion and a second facing portion, wherein the first tangential portion is configured to come in contact with first facing portion at a low speed of rotation of the rotor and the second tangential portion is configured to come in contact with the second facing portion at a high speed of rotation of the rotor, within a variation range of rotational speed; and wherein the first tangential portion is disposed on the one blade and is protruding toward the another blade, and wherein the second tangential portion forms a certain angle (φ) ranging from 90° to 120° with the first tangential portion and is disposed adjacent thereto on the one blade. a variable contact-type vibration damping means disposed on a plurality of bucket blades (20, 30) mounted on an outer peripheral surface of a rotor disk and performing variable contact according to rotational speed of a rotor for damping vibration, wherein the variable contact-type vibration damping means comprises: a first damping member disposed on one blade of the plurality of bucket blades (20, 30); and a second damping member disposed on another blade of the plurality of bucket blades (20, 30) at a position corresponding to the first damping member on the one blade; characterized in that the first damping member comprises a first tangential portion and a second tangential portion and the second damping member comprises a first facing portion and a second facing portion, wherein the first tangential portion is configured to come in contact with first facing portion at a low speed of rotation of the rotor and the second tangential portion is configured to come in contact with the second facing portion at a high speed of rotation of the rotor, within a variation range of rotational speed; and wherein the first tangential portion is disposed on the one blade and is protruding toward the another blade, and wherein the second tangential portion forms a certain angle (φ) ranging from 90° to 120° with the first tangential portion and is disposed adjacent thereto on the one blade. a first damping member disposed on one blade of the plurality of bucket blades (20, 30); and a second damping member disposed on another blade of the plurality of bucket blades (20, 30) at a position corresponding to the first damping member on the one blade; characterized in that the first damping member comprises a first tangential portion and a second tangential portion and the second damping member comprises a first facing portion and a second facing portion, wherein the first tangential portion is configured to come in contact with first facing portion at a low speed of rotation of the rotor and the second tangential portion is configured to come in contact with the second facing portion at a high speed of rotation of the rotor, within a variation range of rotational speed; and wherein the first tangential portion is disposed on the one blade and is protruding toward the another blade, and wherein the second tangential portion forms a certain angle (φ) ranging from 90° to 120° with the first tangential portion and is disposed adjacent thereto on the one blade.