Abstract: A mechanism for aligning a work and a mask, which comprising a camera which picks up an image of a mask mark for aligning a mask having a pattern and an image of a work mark of a work, a control mechanism which recognizes, memorizes, and control the positions of both marks, and, a moving means for moving the work or the mask based on the control signal from the control mechanism to align the shear in the positions of both marks, and which aligns one mark within another mark of both marks, is disclosed. In the case where said one mark to be aligned cannot be recognized, the positions of both marks which have been recognized and memorized at the previous operation are used as pseudo standard, and the amount of the shear in the positions of both marks is carried out to operate the alignment.