PURPOSE: To obtain the titled substance useful as an intermediate for organic chemicals advantageously without danger in handling, fear of corrosion in apparatus, etc., by reacting glyoxylic acid with an alcohol in the presence of a cation exchange resin.

CONSTITUTION: 1mol glyoxylic acid is reacted with 4W20mol, preferably 4.5W10mol alcohol, particularly 1W4C alcohol in the presence of a cation exchange resin as a catalyst at 5W120°C for 2W15hr to afford the titled substance. A sulfonic acid type and strongly acidic resin, carboxylic acid type and weakly acidic resin, phosphoric acid type and weakly acidic resin, etc., may be used as the above-mentioned cation exchange resin in an amount of 10W300wt% based on the glyoxylic acid. Preferably, the glyoxylic acid has 50W95% or more concentration obtained by concentrating a commercially available aqueous solution from the viewpoint of the yield.