In a steel plate having tensile strength of 1 GPa or more at the normal temperature, the steel plate is made, stress decrement (SD) after uniform elongation in the stress-strain diagram obtained by using a tabular specimen of which is not less than 1.8×102 MPa, yield ratio (YR) of which is preferably not lower than 0.7, further preferably not lower than 0.8, and matrix structure of which is composed of martensite or bainite, or mixture of martensite and bainite substantially without proeutectoid ferrite, whereby the tough-ductility is improved on a practically utilizable level, and the steel plate becomes possible to be supplied in large quantities by winding up into a coil.