A detergent box for a washing machine is provided. The detergent box is slidably coupled to a front portion of the washing machine, and has a structure that prevents release of the detergent box from the washing machine even if the washing machine is tilted or shaken, and that facilitates proper placement of the detergent box. The detergent box may include a stopper, and a rib having an elastic slot formed therein. The detergent box holds washing agents, and the dispenser is mounted in the washing machine so as to receive the detergent box therein. The dispenser has a recess for seating the stopper therein as the detergent box is placed in the dispenser. The rib may include an elastic slot to provide an elastic force to the stopper.