PURPOSE: To obtain the subject compound with more improved statistical distribution of alkylene glycol residues than in the known methods, by reacting an aldehyde corresponding to the objective compound with polyalkylene glycol to form an adduct and hydrogenating the adduct.

CONSTITUTION: A compound of the formula, R1CHO (R1 is alkyl or alkenyl having one less carbon atom than R; R is 6-22C alkyl or alkenyl) is reacted with an excess amount of a compound of the formula, HXOH (X is a residue of a polyalkylene glycol comprising at least two alkylene glycol residues) in the presence of an acid catalyst, preferably phosphoric acid at 50-250°C to form an adduct. The adduct is hydrogenated in the presence of a hydrogenation catalyst at 150-300°C and 10-500 bars to give the objective compound of the formula, RXOH useful as surfactants, in high yield with high selectivity, while avoiding the formation of by-products such as dialkyl ethers.