To produce the subject compound on an industrial scale at a low cost without using solvents by separating and purifying a crude reaction product containing the subject compound by thin-film evaporation.

The objective compound is produced by separating and purifying a reaction composition containing an acylhydroxybenzoic acid of the formula (R is a 5-17C alkyl or alkenyl; (n) is 1-3) [preferably a composition produced from a hydroxybenzoic acid (salicylic acid, p-hydroxybenzoic acid, 2,4- dihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, etc.) using a carboxylic acid chloride or a carboxylic acid anhydride (the carboxylic acid in the structure is a 6-18C aliphatic carboxylic acid such as hexanoic acid or heptanoic acid) as an acylation agent] by thin-film evaporation preferably at an operation temperature of 140-220° under a vacuum of 0.01-1mmHg at an evaporation rate of 20-200Kg/hr.m2.