To obtain the subject compound that is useful as a polymerization accelerator and an intermediate for an antihyprtensive agent in high yield by reaction of an aminophenylalkanol with a specific alkylating agent.

N,N-dialkylaminophenylalkanol of formula I (R1 and R2 are each an alkyl; R3 is H, a halogen, cyano, an alkyl, an alkoxy; (n) is 1-4) is prepared by reaction of an aminophenylakanol of formula II with at least 2 moles of dialkyl sulfate of formula III, an alkylating agent. In a preferred embodiment, this process is carried out in an aqueous medium under a normal pressure and the amount of the dialkyl sulfate of formula III is 2.05-2.4 moles per 1 mole of the aminophenylalkanol of formula II. In this process, the dialkyl sulfate is little by little added to the aminophenylalkanol, additionally, the pH of the reaction mixture thereafter is adjusted to 3-5.