A nozzle for a cleaner has a nozzle housing, which has a nozzle base and a drain hole for discharging water from the nozzle housing. The nozzle also has a rotary cleaning unit disposed below the nozzle housing. The rotary cleaning unit has a rotation plate that can be attached to a mop. The nozzle has a driving unit that includes a driving motor for driving the rotary cleaning unit. The nozzle also has a control board for controlling the drive motor. In addition, the nozzle has a water tank detachably mounted on an upper side of the nozzle housing. The water tank stores water and supplies the water to the rotary cleaning unit.