To provide a process for preparing a resorcinol/formaldehyde resin, capable of providing a resorcinol/formaldehyde resin with the excellent flowability and a small resorcinol content, even in the case of employing reused salts.

Provided is a process for producing a resorcinol/formaldehyde resin by subjecting, to a polymerization reaction, a resorcinol and formaldehydes, in the presence of a salts-containing aqueous solution, a 3-6C aliphatic ketone and an acidic catalyst, and separating the mixture after the reaction into an aqueous phase and an organic phase and preparing a resorcinol/hormaldehyde resin from the organic phase, wherein the aqueous phase with the content of the aliphatic ketone adjusted to 0.3 wt.% or less, the alcohol content to 0.1 wt.% or less and the salts concentration to 35-45 wt.% by distilling the separated and collected aqueous phase is utilized as the salts-containing aqueous solution.