PURPOSE: To obtain the subject dye in a directly usable form by dispensing with the intermediate isolation of a non-acetalized azo dye by performing coupling reaction under a specific condition.

CONSTITUTION: A dye represented by formula I [wherein (n) is 0 or 1; R1, R2, R3 and R5 are each independently a hydrogen atom, a 1-4C alkyl, etc.; R4 and R6 are each independently hydrogen atom, a 1-4C alkyl, etc.; R7 is a 1-4C alkyl group; R8 is hydrogen atom or a 1-4C alkyl group; R9 is a 1-18C alkyl group, etc.; and L is a 1-3C alkylene group] is obtained by a method wherein a diazonium salt of an amine represented by formula II is coupled with a coupling component represented by formula III to form a dye represented by formula IV and this dye is reacted with a vinyl ether represented by formula V and, at this time, the coupling reaction is performed in a two-phase reaction mixture containing water and an aromatic hydrocarbon and, succeedingly, the reaction product is reacted with the vinyl ether represented by formula V in the presence of a polybasic carboxylic acid being a catalyst without separating an aq. phase and performing the intermediate isolation of the dye represented by formula IV present in an org. phase.