Grease-enclosed bearing

A grease-enclosed bearing which freely rollably holds a plurality of rolling elements between an inner ring and an outer ring and is filled with a grease composition containing a thickener and a base oil, wherein the thickener is a diurea compound represented by Formula (1) or a mixture thereof, the base oil contains an alkyldiphenyl ether oil and a poly-α-olefin oil as an optional component, and a mass ratio between the alkyldiphenyl ether oil and the poly-α-olefin oil in the base oil is alkyldiphenyl ether oil:poly-α-olefin oil=from 40:60 to 100:0,

• R1-NHCONH—R2-NHCONH—R3 Formula (1)
• wherein at least either one of R1 and R3 is an aromatic hydrocarbon group having a carbon number of 6 to 12, the other one is an aromatic hydrocarbon group having a carbon number of 6 to 12 or an aliphatic hydrocarbon group having a carbon number of 6 to 20, and R2 is an aromatic hydrocarbon group having a carbon number of 6 to 15.