A steel plate for band-shaped die-cutting blades having excellent durability, the steel plate comprising surface layer parts each having a depth of not more than 200 μm from the surface on both sides of the steel plate and a base part located between the surface layer parts in the plate thickness direction, characterized in that : the base part has a chemical composition that contains 0.40 to 0.80 mass% C and 0.10 to 0.50 mass% Nb and has a metallographic structure which comprises bainite or tempered martensite and in which a spherical carbide constituted of cementite is present in the bainite or tempered martensite in an amount of 1.0 vol% or more and a Nb-containing carbide having an equivalent-circle diameter of 0.5 μm or more is present at an existential density of 10.0 or more grains per 900 μm 2 , and the base part has a controlled hardness of from 265 to 450 HV, the surface layer part has a decarburized surface layer constituted of a ferrite single-phase structure and having a thickness of 5 μm or more from the outer surface of the steel plate, and the existential density of the Nb-containing carbide having an equivalent-circle diameter of 0.5 μm or more in a region to the depth of 15 μm from the outer surface of the surface layer part, which is referred to as 15-μm-thick surface layer region is from 0 to 5.0 grains per 900 μm 2 , wherein the existential density of the Nb-containing carbide is determined by observing a region of 4500 μm 2 or more, of a cross section parallel to the plate thickness direction of the steel plate, both in the base part and the 15-pm-thick surface layer region, counting the total number of the grains having equivalent-circle diameter of 0.5 μm or more in the respective region, and converting the number into the density of the grains per 900 μm 2 for the base part and the 15-pm-thick surface layer region, respectively. the base part has a chemical composition that contains 0.40 to 0.80 mass% C and 0.10 to 0.50 mass% Nb and has a metallographic structure which comprises bainite or tempered martensite and in which a spherical carbide constituted of cementite is present in the bainite or tempered martensite in an amount of 1.0 vol% or more and a Nb-containing carbide having an equivalent-circle diameter of 0.5 μm or more is present at an existential density of 10.0 or more grains per 900 μm 2 , and the base part has a controlled hardness of from 265 to 450 HV, the surface layer part has a decarburized surface layer constituted of a ferrite single-phase structure and having a thickness of 5 μm or more from the outer surface of the steel plate, and the existential density of the Nb-containing carbide having an equivalent-circle diameter of 0.5 μm or more in a region to the depth of 15 μm from the outer surface of the surface layer part, which is referred to as 15-μm-thick surface layer region is from 0 to 5.0 grains per 900 μm 2 , wherein the existential density of the Nb-containing carbide is determined by observing a region of 4500 μm 2 or more, of a cross section parallel to the plate thickness direction of the steel plate, both in the base part and the 15-pm-thick surface layer region, counting the total number of the grains having equivalent-circle diameter of 0.5 μm or more in the respective region, and converting the number into the density of the grains per 900 μm 2 for the base part and the 15-pm-thick surface layer region, respectively. <EOS>