Patent Number: 
Section: claims

1. Apparatus for marking multi-layered printed circuit board used in a process for producing multi-layered printed circuit board that includes a plurality of insulated layers and a plurality of conductive layers having a conductive pattern, comprising: a mark that can be detected by X-rays formed on at least one of said layers of said multi-layered printed circuit board,  means for irradiating X-rays on an area containing said mark and detecting the position of the mark,  means for making another mark on an outer layer of said multi-layered printed circuit board based on the position of the mark detected. 2. The apparatus of  claim 1  wherein: claim 1 said means for marking another mark forms said another mark on said conductive layer to be built up next. 3. The apparatus of  claim 1  wherein: claim 1 said means for marking another mark forms said another mark on the resist used for patterning said conductive layer to be built up next. 4. The apparatus of  claim 1  wherein: claim 1 said means for marking another mark forms by color development said another mark on the dry film resist used for patterning said conductive layer to be built up next. 5. The apparatus of  claim 1  wherein: claim 1 said detection means projects the image of said mark in said multi-layered printed circuit board on a fluorescence screen by X-ray irradiation, and photographs the mark by CCD camera.