PURPOSE: To manufacture easily a hot rolled mild steel sheet for carburization and hardening at a low cost by subjecting a continuously cast slab having a low Al content to conventional continuous hot rolling and coiling at a high temp. so as to make the ferrite grains coarse.

CONSTITUTION: A continuously cast slab contg. ≤0.005wt% Al is subjected to conventional continuous hot rolling and coiling at ≥580°C so as to regulate the ferrite grains to grain size No.5 or below. Thus, a hot rolled mild steel sheet having prescribed hardness to a prescribed depth by the processing carburization and hardening is obtd., and the hot rolled mild steel sheet for carburization and hardening can be manufactured by continuous casting.