The present invention relates to an emulsion-based high release additive for a release sheet, the additive being characterized by being obtained by dispersing in water a condensation product (A) obtained by subjecting the following to a dehydration condensation reaction: (A-1) a polydiorganosiloxane which has an average degree of polymerization of 100-300,000 and which has one or more hydroxyl groups or hydrolyzable groups per molecule; and (A-2) a polyorganosiloxane resin, which contains (SiO4/2) units and (R3SiO1/2) units (in the formulae, the R groups each represent independently a monovalent hydrocarbon group having 1-12 carbon atoms and not having an aliphatic unsaturated bond or an alkenyl group having 2-6 carbon atoms) as primary components, in which the molar ratio of (R3SiO1/2) units relative to (SiO4/2) units is 0.6-1.2 and in which the total content of hydroxyl groups and hydrolyzable groups is not lower than 2.1 mass % and lower than 10.0 mass %. The present invention can obtain a silicone cured coating film having a high release force by adding the additive to a curable composition for a release sheet such as a release paper or release film, coating the same on a variety of base materials and curing.