TWI318221B

A process for advantageously producing, in a short period of time, a phenolic novolak resin, in which substantially no unreacted aldehyde remains, by using a continuous reactor, while a generation of higher order condensation products is prevented. In continuously producing the phenolic novolak resin by reacting at least one of phenols with at least one of aldehydes in the presence of an acidic catalyst by using the continuous reactor (10) which has a long reaction tube (12): there are provided a heating zone (26) and a temperature control zone (32) in a longitudinal direction of the reaction tube (12); a mixture of raw materials is heated, at the heating zone (26), to a temperature not less than a temperature, at which a reaction heat is generated; and the mixture, whose temperature is increased by the heating operation and the reaction heat of the addition condensation reaction, is subjected to a cooling operation at the temperature control zone (32) which is located on a downstream side of the reaction tub