A substrate bonding method is provided to perform a vacuum formation process and a bonding process at the same time to reduce the bonding time, and to remove an electrostatic chuck to reduce cost. An upper substrate and a lower substrate are loaded on an upper platen and a lower platen respectively(S20). The upper platen is approached to the lower platen(S21). The upper substrate and the lower substrate are aligned(S22). An inner space of a chamber is exhausted by using a vacuum, and the substrates are bonded(S23).
