To surely correct the shape of a steel strip without causing breakage, even in the case of a thin steel strip or in the case when yield strength of the steel strip is increased and elongation (ductility) is reduced due to work-hardening, when correcting the shape of the steel strip such as flatness by using a tension leveller.

The steel strip 1, after cold rolling, is subjected to heat treatment at the temperature of 70C and 500C with a heat treatment facility 10 and then the shape is corrected by the tension leveller 101.