PURPOSE: To prepare the titled compound in high yield, by hydrogenating glycolic acid or its ester derivative using a Ru complex bonded with a tertiary phosphine through a complex bond, under the condition that the total CO content in the reaction system is not more than equimolar to Ru.

CONSTITUTION: Glycolic acid or its ester derivative (obtained by reacting formaldehyde, CO and water or an alcohol in the presence of an acid catalyst) is made to contact with hydrogen gas to obtain an ethylene glycol compound. The reaction is carried out in the presence of a Ru complex bonded with a tertiary phosphine[e.g. tri(n-butyl)phosphine]through a complex bond. The total CO content in the reaction system is not more than equimolar to Ru. The hydrogen pressure is 5W200kg/cm2G and the reaction temperature is 100W300°C.