A substrate bonding method and apparatus are described. The substrate bonding apparatus is used to bond a first substrate to a second substrate. The bonding apparatus includes a first bonding chuck configured to hold the first substrate on a first surface of the first bonding chuck; a second bonding chuck configured to hold the second substrate on a second surface of the second bonding chuck, the second surface facing the first surface of the first bonding chuck; a seal arranged between the first bonding chuck and the second bonding chuck and adjacent to at least one edge of the first substrate and at least one edge of the second substrate; and a process gas supply device configured to supply a process gas to a bonding space surrounded by the seal.