A window cleaning apparatus according to an embodiment of the present invention includes a first cleaning unit and a second cleaning unit attached on opposite surfaces of a window, respectively, through a magnetic field, and moving on the opposite surfaces of a window. The window cleaning apparatus includes a first magnetic module included in the first cleaning unit, a second magnetic module included in the second cleaning unit, and a control part moving or rotating at least one of the first and second cleaning units when the magnetic field between the first and second cleaning units is out of a normal range.