In a detergent supply apparatus of a drum-type washing machine according to the present invention, detergent supplying units and a softener supplying unit are partitioned and provided in a detergent box and the softener supplying unit is provided with a siphon tube, a siphon cap having an outlet path formed between the siphon tube and the siphon cap is provided with a softener supplying unit, and the softener injecting unit 286 is opened and closed by a softener lid, making it possible to prevent detergent from infiltrating into the inside of the softener supplying unit through the softener supplying unit.