a first sealing member inserted into a first groove formed in a turbine vane platform in a first direction, the first sealing member extending in the first direction;

a second sealing member inserted into a second groove formed in a second direction intersecting the first direction of the turbine vane platform such that an end thereof contacts an upper surface of the first sealing member; and

a third sealing member provided so as to partially extend in the first direction while being partially bent in the second direction at a point where the first and second sealing members are in contact;

wherein

the second sealing member comprises: a plate-shaped sealing body formed with a first thickness, and a sealing head formed with a second thickness greater than the first thickness and having an insertion groove formed in a portion connecting with the sealing body,

the third sealing member comprises: an extension part formed to extend in a first direction and disposed on an upper surface of the first sealing member, a bent part formed by bending in a second direction at a point where the first sealing member and the second sealing member contact, and a protruding tab formed to protrude from an upper surface of the bent part and formed in a shape corresponding to the insertion groove;

the protruding tab is inserted into the insertion groove to restrict the movement of the third sealing member in a third direction lateral to the first direction and the second direction; and

the bent part has a first width in the third direction, and the protruding tab has a second width in the third direction that is less than the first width.