An apparatus for feeding slurry to an external device. The apparatus includes a preparation tank for preparing the slurry. A circulation pipe is connected to the preparation tank to circulate the slurry. A feeding pipe is connected between the preparation tank and the external device to feed the external device with the slurry. A pump sends the chemical solution in the preparation tank to the circulation pipe and the feeding pipe. A concentration detector is arranged downstream to the pump to detect the concentration of the slurry. A controller controls the concentration of the chemical solution in the preparation tank in accordance with the detection value of the concentration detector and controls the feeding of the chemical solution.