The development of an ultrafine grained carbon steel during repetitive shear deformation of side extrusion and the properties after heat treatment were investigated. Side extrusions were carried out at room temperature and the used material was 0.50% carbon steel. The repetitive side extrusions with a constant lateral pressure were carried out up to 3 passes without rotation. The specimens of these steels after 3 passes were annealed at a constant temperature of 600°C changing the treatment time. After side extrusion and heat treatment, the fatigue property was better than that of the as-received material.