In order to develop a new carburizing steel material that realizes an intermediate heat treatment-free process in parts manufacturing, the cold forgeability of the as-rolled steel and suppression of abnormal grain growth of austenite were studied. It was shown that adjustment of Si, Mn and Cr, suppression of dynamic strain aging during cold forging, and an increase of ferrite by controlled rolling contribute to the reduction of deformation resistance. However, Nb precipitation control by fully utilizing mill manufacturing processes was also necessary for suppression of abnormal austenite grain growth. A new steel carburizing was developed by integrating these technologies, making it possible to eliminate annealing before cold forging and normalizing before carburizing simultaneously. Thus, the developed steel is an important innovation in the parts manufacturing process.