Surface roughness of a material called 40Cr was studied using a large-scale pulse electron beam. Different electron beam parameters were tested to see how they affected the surface roughness. The results showed that the surface roughness of 40Cr changed depending on the electron beam parameters. When the number of irradiations increased, the surface roughness decreased for materials with high original roughness, but increased for materials with low original roughness. This means that the surface roughness can be either improved or worsened by using a pulsed electron beam on the material.