Grease composition and rolling bearing

A grease composition comprising:

• base oil;
• a thickener;
• and
• an inorganic additive, wherein
• the base oil is a poly-α-olefin having a base oil kinematic viscosity of 15 to 50 mm2/s at 40° C.,
• the thickener is a diurea expressed by Structural Formula (1),
• R1—NHCONH—R2—NHCONH—R3 (1)
• where R1 and R3 represent functional groups independent of each other and expressed by —CnH2n+1 (n is an integer of 6 to 10), and R2 represents —(CH2)6—, —C6H3(CH3)—, or —C6H4—CH2—C6H4—,
• a content of the thickener is 10 to 22 mass % with respect to a total amount of the base oil and the thickener,
• the inorganic additive is a mixture containing sepiolite and bentonite, and is organically modified, and
• a content of the inorganic additive is 2 to 20 mass % with respect to the total amount of the base oil and the thickener.