Bearing part

A bearing comprising:

• a shaft;
• and
• a rolling element, wherein
• each of the shaft and the rolling element is composed of a steel,
• a quench-hardened layer is formed on a surface of the shaft and the rolling element,
• the quench-hardened layer includes a plurality of martensite crystal grains,
• a ratio of a total area of the plurality of martensite crystal grains in the quench-hardened layer is more than or equal to 70%,
• the plurality of martensite crystal grains are classified into a first group and a second group,
• a minimum value of crystal grain sizes of the martensite crystal grains belonging to the first group is larger than a maximum value of crystal grain sizes of the martensite crystal grains belonging to the second group,
• a value obtained by dividing a total area of the martensite crystal grains belonging to the first group by the total area of the plurality of martensite crystal grains is more than or equal to 0.5,
• a value obtained by dividing, by the total area of the plurality of martensite crystal grains, a total area of the martensite crystal grains belonging to the first group except for a martensite crystal grain that has a minimum crystal grain size and that belongs to the first group is less than 0.5,
• an average grain size of the martensite crystal grains belonging to the first group is less than or equal to 0.97 μm,
• the steel is high-carbon chromium bearing steel SUJ2 defined in JIS,
• the quench-hardened layer contains nitrogen, and an average nitrogen concentration of the quench-hardened layer is more than or equal to 0.05 mass % and less than or equal to 0.15 mass % between the surface and a position at a distance of 10 μm from the surface.