The present invention provides a novel mold release agent composition which can cope with a higher temperature range than that of the conventional mold release agent composition. That is, a mold release agent composition for use in casting of the present invention contains a silicone oil and a solvent, wherein the silicone oil contains 30% by mass or more of a first silicone oil represented by the formula (1) and 70% by mass or less of a second silicone oil represented by the formula (2), with respect to the total amount of the silicone oil. In the formula (1), R1 is an alkyl group having 1 to 6 carbon atoms; and R2 is an aralkyl group, a phenyl group, or a mercaptoalkyl group. In the formula (2), R3 is an alkyl group having 8 or more carbon atoms; and R4 is an aralkyl group, a phenyl group, or a mercaptoalkyl group.