PROBLEM TO BE SOLVED: To provide an antifoam excellent in antifoam property generally.SOLUTION: The antifoam includes an alkylene oxide appendage expressed by the general formula (1) as an essential component: (1) RO-[(PO)x/(EO)y]-H. (R may be selected from an alkyl group or an alkenyl group and may be formed of a straight structure or a branch structure. The R includes 30-70 mass% of a mass ratio having a carbon number of 8-13, and includes 30-70 mass% of a mass ratio having a carbon number of 16-20. PO is an oxypropylene group, and an EO is an oxyethylene group, x and y express an average addition mol number, x=1-40 and y=0-20. [(PO)x/(EO)y] is a polyoxy alkylene group formed by random addition and/or block addition.)
