To provide a masking device in which it is possible to carry out a vacuum vapor deposition in manufacturing an organic EL element with high productivity and high-precision patterning.

This is constituted so that the second metal mask 13 provided with a screen part 13A with a constitution that numerous minute slits with numerous minute distances are arranged in parallel on a base plate 12 which also serves as the first metal mask equipped with a plural number of windows 18 to regulate the range of the vapor deposition, so that one end of this is fixed to the base plate 12 by a mask clamp 20, so that the other end is fixed to a slider 23, so that a tensile force is given to the screen part 13A of the second metal mask by giving a spring force to the slider 23 by compression coil spring 30, and so that the slit is maintained in a straight state with a prescribed pitch. A high-precision pattern can be formed on a substrate with a multiple units by arranging and carrying out the vapor deposition on the substrate 17 on this second metal mask 13.