Provided is a silicone based anti-foaming agent oil compound that has not only superior anti-foaming speed but also anti-foaming performance that does not degrade with repeated use or use over a long period. The silicone based anti-foaming agent oil compound comprises: (A) an essentially hydrophobic organopolysiloxane with a viscosity at 25° C. of 2,500 to 50,000 mPa·s: 20 to 80 parts by mass; (B) a hydrophobic organopolysiloxane or cyclic organopolysiloxane having silanol groups at least at both terminals: 20 to 80 parts by mass; (C) a silane or silane condensation product: 1 to 10 parts by mass; and (D) a fine powder silica with a specific surface area of 50 m2/g or more: 2 to 10 parts by mass; where the total amount of (A) and (B) combined is 100 parts by mass. Also provided is a method for manufacturing the silicone based anti-foaming agent oil compound.