An antifoaming agent comprising: (A) an organopolysiloxane having a hydrolysable group shown by the formula on at least one silicon atom of an organopolysiloxane segment constituting a main chain and containing siloxy units shown by the formula at an amount of at least 10 mol% of the total, wherein X represents a divalent hydrocarbon group having 1 to 10 carbon atoms; and R each independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 4 carbon atoms, wherein R 1 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms; and R 2 represents an organic group having an aryl group and 6 to 12 carbon atoms, optionally containing an oxygen atom or a halogen atom; (B) a non-linear organosilicon resin other than the organopolysiloxane of component (A) , the non-linear organosilicon resin comprising: a R 5 3 SiO 1/2 unit, wherein R 5 represents a monovalent hydrocarbon group, a hydrocarbonoxy group, or a hydroxy group, and 10 mol% or more of R 5 is a monovalent hydrocarbon group; and an SiO 2 unit, wherein R 5 3 SiO 1/2 unit/SiO 2 unit=0.4 to 2.5; and (C) a hydrophobic filler, wherein the component (A) is an organopolysiloxane shown by the following general formula having a kinematic viscosity of 200 to 50,000 mm 2 /s at 25°C measured with a Cannon-Fenske viscometer, where R 1 and R 2 are as described above; R 3 represents the hydrolysable group shown by the formula ; R 4 is the same as R 1 , or a group selected from the hydrolysable group of formula , a hydroxy group and a methoxy group; "n" represents an integer of 5 to 10,000; "m" represents an integer of 1 to 2,000; and "1" represents an integer of 1 to 20. (A) an organopolysiloxane having a hydrolysable group shown by the formula on at least one silicon atom of an organopolysiloxane segment constituting a main chain and containing siloxy units shown by the formula at an amount of at least 10 mol% of the total, wherein X represents a divalent hydrocarbon group having 1 to 10 carbon atoms; and R each independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 4 carbon atoms, wherein R 1 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms; and R 2 represents an organic group having an aryl group and 6 to 12 carbon atoms, optionally containing an oxygen atom or a halogen atom; (B) a non-linear organosilicon resin other than the organopolysiloxane of component (A) , the non-linear organosilicon resin comprising: a R 5 3 SiO 1/2 unit, wherein R 5 represents a monovalent hydrocarbon group, a hydrocarbonoxy group, or a hydroxy group, and 10 mol% or more of R 5 is a monovalent hydrocarbon group; and an SiO 2 unit, wherein R 5 3 SiO 1/2 unit/SiO 2 unit=0.4 to 2.5; and (C) a hydrophobic filler, wherein the component (A) is an organopolysiloxane shown by the following general formula having a kinematic viscosity of 200 to 50,000 mm 2 /s at 25°C measured with a Cannon-Fenske viscometer, where R 1 and R 2 are as described above; R 3 represents the hydrolysable group shown by the formula ; R 4 is the same as R 1 , or a group selected from the hydrolysable group of formula , a hydroxy group and a methoxy group; "n" represents an integer of 5 to 10,000; "m" represents an integer of 1 to 2,000; and "1" represents an integer of 1 to 20. the component (A) is an organopolysiloxane shown by the following general formula having a kinematic viscosity of 200 to 50,000 mm 2 /s at 25°C measured with a Cannon-Fenske viscometer, where R 1 and R 2 are as described above; R 3 represents the hydrolysable group shown by the formula ; R 4 is the same as R 1 , or a group selected from the hydrolysable group of formula , a hydroxy group and a methoxy group; "n" represents an integer of 5 to 10,000; "m" represents an integer of 1 to 2,000; and "1" represents an integer of 1 to 20. <EOS>