The present invention relates to a clothing treatment device. The clothing treatment device comprises a cabinet having an open part provided at the front thereof: a door assembly for opening and closing the open part; a first clothing treatment room, which is provided inside the cabinet so as to provide a space for accommodating clothing therein, and communicates with the outside of the cabinet through the open part; and a machinery room for circulating steam or air in the first clothing treatment room, wherein the door assembly comprises; an assembly housing which opens and closes the opened front surface of the cabinet and which has a space of a second clothing treatment room therein; and an assembly door for opening and closing, at the front of the cabinet, the second clothing treatment room formed in the assembly housing.