2-Carboxydibenzoylmethanes of the following formula ##STR1## in which R.sub.1 and R.sub.2 are independently a substituent joined to any position of the benzene nucleus and represent a hydrogen atom, a halogen atom, a linear or branched alkyl or alkenyl group having from 1 to 18 carbon atoms, or a linear or branched, saturated or unsaturated alkoxy group having from 1 to 18 carbon atoms, m is an integer of from 1 to 4, and n is an integer of from 1 to 5 are prepared inexpensively with ease in high yield by a novel process characterized by reaction between phthalic anhydrides and acetophenones in the presence of bases. The 2-carboxydibenzoylmethanes are useful as an inhibitor of the root geotropic response of plants or a growth regulator for plants, or a stabilizer for halogen-containing resins.