Washing machine

Provided is a washing machine in which a treatment agent tank and a treatment agent cartridge are arranged adjacent to each other, the treatment agent tank can be easily taken out, and the operability can be improved. The washing machine includes: an outer box formed in a box shape; the water containing barrel is arranged in the outer box; an accommodating part which is arranged in the outer box and is provided with an opening part which is formed by opening the top surface part side of the outer box; a treatment agent cartridge for receiving the input of the washing treatment agent used in the primary operation and supplying the input washing treatment agent to the water tub; and a treatment agent tank capable of storing a washing treatment agent used in multiple operations. The accommodating part can accommodate the processing agent box and the processing agent tank in the accommodating part in a horizontal direction. The processing agent tank can be attached to or detached from the accommodating part in a