Presented is a method for increasing coke oven gas which can maximize the amount of coke oven gas generated, by optimizing steam input time. This method is characterized in that, in order that a water-gas reaction can progress at at least 500 DEG C during a step for carbonizing coal in a carbonizing chamber in a coke oven, steam is inputted to a gas way in the carbonizing chamber of the coke oven, the steam input point is brought forward so as to be before the point at which the coke oven gas generation amount is optimal, and thus the steam input time is increased, maximizing the reaction with carbon present in the carbonizing chamber in the coke oven.