A method for producing a hetero-type monodisperse polyethylene glycol, which includes (A) carrying out a nucleophilic substitution reaction between a compound of formula (2) and a compound of formula (3) so as to satisfy expression (F1) to obtain a compound of formula (4), (B) of carrying out a Michaels addition reaction of a compound of formula (5) to the compound of formula (4) at a temperature condition of 10° C. or lower to obtain a compound of formula (6), (C) detritylating or debenzylating the compound of the formula (6) to obtain a reaction product containing a compound of formula (7), (D) purifying the compound of formula (7) from the reaction product, (E) reacting the compound of formula (7) with phthalimide and performing dephthalimidation to obtain a compound of formula (8), and (F) subjecting the compound of formula (8) to an acid hydrolysis treatment to obtain a compound represented by formula (1).