A processing apparatus of a stack is provided. The stack includes two substrates attached to each other with a gap provided between their end portions. The processing apparatus includes a fixing mechanism that fixes part of the stack, a plurality of adsorption jigs that fix an outer peripheral edge of one of the substrates of the stack, and a wedge-shaped jig that is inserted into a corner of the stack. The plurality of adsorption jigs include a mechanism that allows the adsorption jigs to move separately in a vertical direction and a horizontal direction. The processing apparatus further includes a sensor sensing a position of the gap between the end portion in the stack. A tip of the wedge-shaped jig moves along a chamfer formed on an end surface of the stack. The wedge-shaped jig is inserted into the gap between the end portions in the stack.