Grease composition and rolling bearing

A grease composition comprising:

• an ester base oil in an amount of 78 to 88 mass % based on a total amount of the grease composition;
• and
• a thickener in an amount of 10 to 17 mass % based on the total amount of the grease composition,
• wherein the thickener contains diurea expressed by the following formula (1):
• R1—NHCONH—C6H4—CH2—C6H4—NHCONH—R2 (1),
• in which R1 and R2 each independently represents one of:
• (A) a cyclohexyl group;
• (B) an octyl group;
• and (C) an octadecyl group, and
• wherein the diurea is arranged so that the cyclohexyl group (A) is 5 to 35 mol %, the octyl group (B) is 50 mol % or higher, a total of the cyclohexyl group (A) and octyl group (B) is 55 to 95 mol %, and the remainder is the octadecyl group (C), based on a total of R1 and R2,
• wherein the grease composition has a bearing rotational torque corresponding to two test ball bearings of 14 mN-m or less, when the grease composition was enclosed in 6202 which is the ball bearing having an inner ring, an outer ring and a plurality of balls, a cage and two non-contact seals, the amount of the enclosed grease reached 40 volume % relative to the volume of a space excluding the balls and the cage from a space surrounded by the inner ring, the outer ring and the seals, and wherein the grease exhibits an oil leakage of 9% or less when enclosed in a 6309ZZ test bearing, the amount of the enclosed grease reaching 20% by volume relative to the volume of a space excluding balls and a cage from a space surrounded by an inner ring, outer ring and shield plates, and the test bearing rotated at 6,000 min−1 at 150° C. in outer ring temperature for 15 hours.