A mobile robot is disclosed, including a body, a mop module installed on the body and being configured to clean using water, a water tank removably disposed in the body and being configured to store water to be supplied to the mop module, and a detachable water tank module installed on the water tank. The water-tank detachable module includes a hook engaged with or coupled to the body and an operation button disposed on a surface of the water tank to operate the hook.