To obtain coffee beverage such as can coffee having excellent coffee feeling and milk feeling without causing separation or precipitation of milk, etc., due to retort treatment by reacting a prepared solution obtained by adding milk, etc., and sugar to coffee extract with metal protease or serine protease and subjecting the treated liquid to retort treatment.

A prepared liquid obtained by adding milk, etc., and sugar to coffee extract is reacted with a metal protease or serine protease and the treated liquid is subjected to retort treatment. The reacting time can be shortened by adding ≥0.2wt.% metal protease to a milk protein contained in milk, etc., in the case of metal protease adding ≥0.002wt.% serine protease to the milk protein in the case of serine protease.