PURPOSE: To improve the processability and tensile strengh of a steel sheet by specifying the content of C, Si, Mn and Al in the steel sheet, specifying the finish rolling temp. and cooling conditions and executing coiling to incorporate a specified amt. of retained austenite therein.

CONSTITUTION: A steel slab constituted of, by mass, 0.10 to 0.20% C, 0.80 to 1.60% Si, 3.0 to 6.O% Mn and ≤0.50% Al, and the balance Fe with inevitable impurities is subjected to hot rolling at a finishing temp. of 750 to 900°C. It is cooled down to 400 to 650°C at 10 to 30°C/sec cooling rate, is coiled and is thereafter air-cooled. In this way, the hot rolled thin steel sheet contg. ≥10% retained austenite and excellent in the balance of strength and elongation can be obtd.