A washing machine comprising: a cabinet; a tub provided inside the cabinet to store water therein; and a detergent supply apparatus configured to supply detergent to the tub, the detergent supply apparatus including: a housing provided to have an opening at an upper side of the tub; a detergent box provided to be inserted into and withdrawn from the housing through the opening; a detergent pump fixed to the housing to allow the detergent box to be docked thereonto or undocked therefrom, the detergent pump configured to, upon the detergent box being docked onto the detergent pump, suction a detergent from the detergent box and discharge the detergent to the housing; characterized in that the washing machine further comprises: an auxiliary tank provided in the housing to store water therein, and including: a water storage portion in which water is stored, and a drain port through which the water stored in the water storage portion is drained to the bottom of the housing to prevent the detergent from hardening on the bottom of the housing. a cabinet; a tub provided inside the cabinet to store water therein; and a detergent supply apparatus configured to supply detergent to the tub, the detergent supply apparatus including: a housing provided to have an opening at an upper side of the tub; a detergent box provided to be inserted into and withdrawn from the housing through the opening; a detergent pump fixed to the housing to allow the detergent box to be docked thereonto or undocked therefrom, the detergent pump configured to, upon the detergent box being docked onto the detergent pump, suction a detergent from the detergent box and discharge the detergent to the housing; characterized in that the washing machine further comprises: an auxiliary tank provided in the housing to store water therein, and including: a water storage portion in which water is stored, and a drain port through which the water stored in the water storage portion is drained to the bottom of the housing to prevent the detergent from hardening on the bottom of the housing. a housing provided to have an opening at an upper side of the tub; a detergent box provided to be inserted into and withdrawn from the housing through the opening; a detergent pump fixed to the housing to allow the detergent box to be docked thereonto or undocked therefrom, the detergent pump configured to, upon the detergent box being docked onto the detergent pump, suction a detergent from the detergent box and discharge the detergent to the housing; characterized in that the washing machine further comprises: an auxiliary tank provided in the housing to store water therein, and including: a water storage portion in which water is stored, and a drain port through which the water stored in the water storage portion is drained to the bottom of the housing to prevent the detergent from hardening on the bottom of the housing. an auxiliary tank provided in the housing to store water therein, and including: a water storage portion in which water is stored, and a drain port through which the water stored in the water storage portion is drained to the bottom of the housing to prevent the detergent from hardening on the bottom of the housing.