PURPOSE: To selectively obtain only the compound by using an acidic ion- exchange resin or an aqueous acid as a catalyst and condensing N- phenylalkylcarbamate with a methylating agent in a non polar aprotic solvent and filtrating a condensation product at a specified temp.

CONSTITUTION: A 4,4-methylene-bis-(N-phenylalkylcarbamate) of formula II is obtained by condensing an N-phenylalkylcarbamate of formula I (R is ≤3C alkyl) with a methylating agent in the presence of an acidic ion-exchange resin or an aqueous acid (e.g. sulfuric acid, phosphoric acid or the like) as a catalyst and in a non polar aprotic solvent such as water, benzene, toluene, xylene or the like and filtrating the condensation product at a temperature greater than the melting point of the compound of formula I which is the raw material to separate the objective product. The compound of formula II is a precursor of 4,4-diphenylmethanediisocyanate useful for raw material of polyurethane. In this process, undesirable by-products are scarcely formed to achieve high reactivity and selectivity.