Clothes treatment apparatus and control method therefor

A laundry treating apparatus comprising:

• a tub configured to hold wash water;
• a drum rotatably supported in the tub, the drum comprising a shaft disposed perpendicular with the ground;
• a sub-drum detachably mounted to the drum, the sub-drum being configured to wash laundry independently from the drum, wherein
• the sub-drum comprises:
• a sub-drum body having a container-like shape configured to accommodate wash water and laundry;
• a sub-drum cover coupled to a top of the sub-drum body and having a laundry introduction opening for loading the laundry, wherein the sub-drum cover comprises,
• a lower cover that is one of integrally formed with the sub-drum body or coupled to the sub-drum body, wherein an inlet hole and an outlet hole are defined in the lower cover;
• an upper cover coupled to a top surface of the lower cover;
• a chamber being defined in between the lower cover and the upper cover;
• a discharging area defining a discharging path through which wash water is selectively discharged from the sub-drum by a centrifugal force generated by rotation of the sub-drum, wherein the discharging area comprises,
• the chamber defined independently from a space in which washing is performed, the chamber being configured to receive wash water from the sub-drum;
• the inlet hole of the lower cover being configured to draw the wash water into the chamber;
• and
• the outlet hole of the lower cover being configured to discharge the wash water from the chamber outside the sub-drum;
• and
• a check valve configured to selectively open and close the discharging area based on an external force applied to the check valve by the centrifugal force generated by the rotation of the sub-drum,
• wherein the upper cover is configured to apply a downward pressure to one side of the check valve to fix the check valve when the upper cover is coupled to the lower cover.