A method of smelting copper includes: a generating step of generating blister and slag from copper matte by charging the copper matte into a smelting furnace and oxidizing the copper matte; a first refining step of refining another blister from the slag by reduction in an electrical furnace; and a charging step of charging the slag into one of the smelting furnace or another smelting furnace for treating copper concentrate and generating matte as repeating flux if copper grade of slag generated in the first refining step is higher than 0.8 weight %.