The present invention relates to a process for manufacturing a martensitic stainless steel, comprising the following heat-processing steps: (1) the steel is heated to a temperature above the austenization temperature TAUS of the steel; next, the steel is quenched until the temperature of the hottest part of the steel is less than or equal to a maximum temperature Tmax and greater than or equal to a minimum temperature Tmin, the cooling rate being sufficiently rapid for the austenite not to be transformed into a ferrite-pearlite structure; (2) the steel undergoes a first tempering treatment and is then cooled until the temperature of the hottest part of the steel is less than or equal to the maximum temperature Tmax and greater than or equal to the minimum temperature Tmin; and (3) the steel undergoes a second tempering treatment after which it is cooled down to room temperature TA. The maximum temperature Tmax is below the temperature MF' of the end of the martensitic transformation of the interdendritic spaces in the steel upon cooling and, in each of steps (1) and (2), the following substep is carried out: (omega) as soon as the temperature of the hottest part of the steel reaches the maximum temperature Tmax, the steel is immediately reheated.