Dissolution behavior of cementite in eutectoid steels with pearlitic and spheroidite structures by severe plastic deformation was studied. Applying a long time milling, cementite dissolved completely and matrix turned out to be nanocrystalline ferrite. By a ball drop deformation (at high strain rates), heavily deformed layers in which cementite dissolves completely or partially were produced. By applying pulsed laser irradiation, re-austenitized zone which transformed to fresh martensite during quenching was produced. The boundary between the re-austenitized zone and matrix exhibited similar microstructure with that observed in specimens subjected to a ball drop deformation. It was suggested that the dissolution of cementite by heavy deformation at high strain rates are probably due to thermal effect, that is, re-austenitization.