Sliding member, clutch plate, and production methods thereof

A method of producing a sliding member including a base material portion that is formed of steel, a nitrogen diffusion layer that is formed to have a thickness of 10 μm to 50 μm on a surface side of the base material portion, and a nitrogen compound layer that is formed to have a thickness of 10 μm to 50 μm on a surface side of the nitrogen diffusion layer, and that constitutes an outermost surface,

• wherein the nitrogen compound layer and the nitrogen diffusion layer are formed by performing:
• a first heating process of performing heat treatment on a material formed of steel in an ammonia atmosphere at a temperature of 570° C. to 660° C.;
• a second heating process of performing heat treatment on the material in a non-oxidizing and non-ammonia atmosphere at a temperature of 660° C. to 690° C. subsequently to the first heating process, the temperature in the second heating process being higher than the temperature in the first heating process;
• and
• an oil cooling process of performing oil cooling treatment at an oil temperature of 60° C. to 80° C. subsequently to the second heating process.