C≤0.10 mass %,

Si≤0.50 mass %,

3.0≤Mn≤8.0 mass %,

P≤0.30 mass %,

S≤0.30 mass %,

7.0≤Ni≤9.9 mass %,

18.0≤Cr≤28.0 mass %,

1.0≤Mo≤3.0 mass %,

0.03≤V≤0.50 mass %,

0.0003≤B≤0.0300 mass %,

0.0001≤Ca≤0.0300 mass %,

0.35≤N≤0.80 mass %,

W≤2.0 mass %,

Zr≤0.20 mass %,

Cu≤0.5 mass %,

Al≤0.10 mass %, and

O≤0.050 mass %,

with a balance being Fe and unavoidable impurities, and

having a number density of coarse alloy carbonitrides of 3×10⁵ pieces/mm² or less,

having a crystal grain size number of an austenite crystal grain being 6.8 or less, and

having a relative wear amount ratio being 0.40 or more, wherein

the “coarse alloy carbonitride” refers to an alloy carbonitride having an equivalent circle diameter of more than 1,000 nm, and

the relative wear amount ratio is defined by W₀/W₁; here W₀ events a flank wear amount of a cemented carbide tool with no coating treatment and corresponding to P20 in the JIS Standard when a bar-shaped test piece having a chemical composition corresponding to SUS316 in the JIS Standard is subjected to a peeling processing with the cemented carbide tool under a condition of cutting speed of 100 m/min, a feed of 0.2 mm/rev, a cut of 1.0 mm, and no lubricating oil; and W₁ represents a flank wear amount of the same cemented carbide tool when a bar-shaped test piece having the above-described chemical composition is subjected to the same peeling processing with the cemented carbide tool under the same condition.