A cooling structure of a turbine blade for cooling a turbine blade (10) exposed to hot gas (1) by cooling air (2) having a temperature lower than the hot gas. The turbine blade (10) comprises an outer surface (11), an inner surface (12) opposite to the outer surface, a plurality of film-cooling holes (13) for cooling a film by blowing the cooling air from the inner surface onto the outer surface, and a plurality of heat-transfer promotion projections (14) formed integrally with the inner surface and projecting inward. The turbine blade further includes a hollow cylindrical insert (20) which is positioned on the side more inner than the inner surface and into which the cooling air is supplied, and the insert has plural impingement holes (21) for impingement-cooling of the inner surface (12).
