Disclosed is a robot system including: a robot cleaner configured to perform wet cleaning in a cleaning zone; a server configured to communicate with the robot cleaner and perform control of the robot cleaner; and a user terminal configured to be in association with the robot cleaner, and control the robot cleaner as an application for the control of the robot cleaner is activated, wherein the robot cleaner includes: a main body configured to form an outer shape; a pair of rotary mop modules configured to be rotatably installed in the main body, move the main body while rotating, and have a mop cloth attached to a rotating plate of a lower portion; a drive motor configured to rotate the pair of rotary mop modules; a mop detecting unit configured to detect an error state of the mop cloth attached to the rotating plate and output a detection signal; and a controller configured to determine the error state of the mop cloth according to the detection signal from the mop detecting unit, and control driving of the rotary mop module.