An alcohol, e.g. methanol, carbon monoxide and oxygen are allowed to react in a gas phase in the presence of a solid catalyst comprising a catalyst component, for instance, containing halogen and copper atoms supported on a solid support. The alcohol and carbon monoxide contents of the reactor feed gas are controlled at 1 to 20 volume % and 70 to 95 volume %, respectively. Because the alcohol and carbon monoxide contents of the feed reactant gas are thus controlled, side reactions are considerably inhibited and the object carbonic diester is produced with high selectivity.