There is provided a grease composition, in which a grease film on the surface of the applied part is made thicker compared with conventional grease compositions, this thickness is maintained for a long period of time, and as a result, a longer service life against seizure compared with conventional grease compositions is assured. The grease composition comprises a base oil and a thickener, wherein the thickener is a diurea compound obtained by allowing an amine mixture comprising alkylphenylamine, an alkyl group of which has 8 to 16 carbon atoms, and cyclohexylamine, to react with a diisocyanate compound, and an amount of cyclohexylamine in the total amount of the alkylphenylamine and cyclohexylamine is from 91 to 99% by mole.