A method of manufacturing a ceramic/metal composite structure includes the steps of: performing a multi-stage pre-oxidizing process on the copper sheet; placing the copper sheet on a ceramic substrate; and heating the copper sheet and the ceramic substrate to a joining temperature to join the copper sheet and the ceramic substrate together to enhance interface strength between the copper sheet and the ceramic substrate according to the multi-stage pre-oxidizing process. The multi-stage pre-oxidizing process includes a first stage of pre-oxidizing process and a second stage of pre-oxidizing process, and the first and second stages of pre-oxidizing processes are performed in atmospheres with different oxygen partial pressures and at different temperatures.