An apparatus for attaching two substrates to one another includes a lower chamber that holds a first substrate and an upper chamber that holds a second substrate. The upper and lower chambers are brought together to provide a space in which an attaching process is performed. Chamber transportation mechanisms are located at corners of the lower chamber and serve to move the lower chamber up toward the upper chamber so that it can be coupled with the upper chamber. Guide parts are also formed on side surfaces of the lower chamber to guide movement, and to reduce deformation of the chamber when pressure differentials act to deform the sides of the chamber.