An object of the present invention is to provide air cooling equipment for a heat treatment process for a martensitic stainless steel pipe, which is capable of shortening the time required for the heat treatment process by enhancing the cooling efficiency at the time when the inner surface of steel pipe is air cooled in the heat treatment ent process.Air cooling equipment 100 for a heat treatment process for a martensitic stainless steel pipe P in accordance with the present invention comprises: a conveying device 10 for intermittently conveying the steel pipe P in the direction substantially at right angles to the longitudinal direction of the steel pipe P; and an air cooling device 20 provided with a nozzle 21 for spraying air Bi toward the inner surface of the steel pipe P, the nozzle 21 being arranged along the longitudinal direction of the steel pipe P at a stop position of the steel pipe P intermittently conveyed by the conveying device 10 so as to face to an end of the steel pipe P.