PURPOSE: To increase the hardness and fatigue strength of a die and to prolong the service life of a die by ejecting specified particulate matter at a specified speed to a rolling plane of action of the die and removing the tensile stress set up on the plane of action to set up the compressive stress.

CONSTITUTION: Fine particulate matter of ≤0.1mm is ejected or projected on the plane of rolling action of the die at a speed of >10m/min. Positive tensile stress set up on the plane of action is removed, the positive compressive stress is set up and the surface hardness is elevated. The hardness of form chevron of the die is increased by conducting said treatment and working, at the same time, the fatigue strength is increased to repeatedly added external force.