Silicon nitride member, method for manufacturing the same, and cutting tool

A silicon nitride member comprising a substrate formed by sintering of a silicon nitride material, and a hard film formed on a surface of said substrate, said silicon nitride member characterized in that:

• when the amount of a grain boundary phase as measured at a central portion of said substrate is taken as 100% by volume, at least one of the following conditions (1) to (5) is satisfied:
• (1) the amount of a grain boundary phase as measured in the vicinity of a depth of 100 μm from the surface of said substrate is less than 30% by volume;
• (2) the amount of a grain boundary phase as measured in the vicinity of a depth of 200 μm from the surface of said substrate is 30% to 50% by volume;
• (3) the amount of a grain boundary phase as measured in the vicinity of a depth of 300 μm from the surface of said substrate is 50% to 70% by volume;
• (4) the amount of a grain boundary phase as measured in the vicinity of a depth of 400 μm from the surface of said substrate is 70% to 85% by volume;
• and
• (5) the amount of a grain boundary phase as measured in the vicinity of a depth of 500 μm from the surface of said substrate is 85% to 100% by volume.