A robot cleaning system is capable of performing automatic cleaning and manual cleaning with a minimal number of devices. The robot cleaning system includes a first cleaning unit to perform automatic cleaning while moving by itself in an area to be cleaned, and a second cleaning unit to perform manual cleaning while being coupled to the first cleaning unit as it is moved by a user in an area to be cleaned. Each of the first and second cleaning units contains a blower and dust collector to vacuum. The first cleaning unit has a dust outlet to deliver dust to the second cleaning unit when the first cleaning unit is coupled to the second cleaning unit via the dust outlet of the first cleaning unit, a connector, and the connection port of the second cleaning unit.