A cooling structure for a turbine airfoil includes: a lattice structure body formed such that a first rib set and a second rib set arranged in a cooling passage are stacked on each other in a lattice pattern; and lattice communication portions that allow passages formed between ribs of the first rib set to communicate with passages formed between ribs of the second rib set. Each of the first and second rib sets has rib walls each including a pair of ribs that are inclined in directions opposite to each other relative to an imaginary boundary line extending in a movement direction of a cooling medium and that are in contact with each other on the imaginary boundary line. A plurality of lattice communication portions are formed between two lattice communication portions at opposite end portions of each rib that forms the rib wall.