PURPOSE: To efficiently recover copper component from a converter slag containing much iron oxide and silicate ore.

CONSTITUTION: In a floatation method for recovering the copper content from the converter slag in a copper smelting process, the copper slag is crushed and water is added at the time of crushing and/or after crushing to make slurry, and acid is added into the obtd. slurry to adjust pH of the slurry to 6.5-7.5. From a first step floatation, froth concentrating the copper content in the converter slag is recovered and also, the remained deposited ore is further crushed and the water is added at the time of crushing and/or after crushing to make the slurry. The acid or alkali is added into the obtd. slurry to adjust the pH of slurry to 7.5-8.5 to execute a second floatation. The floatation method of the converter slag is composed of the recovering of the froth concentrating the copper content at the above first step floatation and the second step floatation.