The present invention provides a method for cleansing a glass substrate and a device for performing the method. The method includes: (1) providing a transport platform (20) and a glass substrate to be cleansed (40); (2) placing a glass substrate to be cleansed (40) on the transport platform (20); (3) providing two air blowing devices (60); (4) the two air blowing devices (60) blowing air flows toward the lass substrate to be cleansed (40) to have impurities (42) that are attached to the glass substrate to be cleansed (40) detached from the glass substrate (40); (5) providing a suction device (80), the suction device (80) comprising an air drawing device (82) and a magnetic attraction device (84); (6) the air drawing device (82) drawing air from the glass substrate to be cleansed (40) and the magnetic attraction device (84) generating a magnetic attraction force to magnetic impurities on the glass substrate to be cleansed (40) so as to draw the impurities (42) attached to the glass substrate to be cleansed (40) into the suction device (80).