To provide a method of manufacturing steel casting parts made of martensitic stainless steel which can satisfactorily keep dimensional accuracy of cast material molded into a prescribed shape by precision casting and is excellent in fatigue strength.

The method of manufacturing the steel casting parts made of martensitic stainless steel is provided, by which the cast material composed of the martensitic stainless steel containing 0.2 mass% C or higher is molded into the prescribed shape by the precision casting and a soaking treatment is applied to the cast material while applying a hot isostatic pressing treatment thereto, thereby obtaining the steel casting parts made of martensitic stainless steel. Preferably, the treating temperature is set to at least the perfect austenitizing temperature or higher of the martensitic stainless steel, and the treating pressure is set to the tensile strength or higher of the martensitic stainless steel at this treating temperature.