PURPOSE: To effectively conduct the adjustment of the productivity and, at the same time, to prevent the lowering in the quality of tar, by emptying part of carbonization chambers and connecting the empty oven to an operating carbonization chamber to pass a substance produced during coal carbonization in the operating carbonization chamber through the empty oven.

CONSTITUTION: In operating a coke oven, part of carbonization chambers are emptied to lower the productivity, and the empty oven is connected to the operating carbonization chamber to pass a substance produced during coal carbonization in the operating carbonization chamber through the empty oven, thereby improving the quality of tar. This method enables a remarkable lowering in the minimum productivity in the production of coke, produces no excessive coke as opposed to the conventional process, and minimizes the damage to the oven body.