The development of compact electron storage rings have already started in West Germany (BESSY) and France (Neyrpic Corp.) and recently in Japan and the USA. On February 28, 1986 the ETL (Electrotechnical Lab.) first completed, jointly with the Sumitomo Electric Industries Ltd., a small test ring “NIJI-I” and succeeded in storing a 160-MeV beam of more than 340mA in March 1987. A superconducting type compact ring will be completed by them in 1989. The NTT Corp. and the Sumitomo Heavy Industries Ltd. are also developing superconducting type compact rings. The wide applicability of SR depends on its several important properties such as high intensity of more than four orders compared with the conventional sources, broad spectral range from infrared to X-ray region, narrow divergence of the order of milli-radian. Although the present applications of SR concentrate in the analysis and evaluation of the properties of materials, recently much attention has come to be paid to the applications of SR and wiggler X-rays to ULSI lithography, CVD technology and medical diagnosis. The conventional storage ring can't achieve uniform and wide-area exposure of SR for ULSI lithography because of the vertically narrow divergence of SR. However, the electron undulating ring has made possible uniform large-area exposure of SR by a factor of more than five. The development of a compact X-ray ring measuring about 10m in mean diameter is also expected to realize the medical diagnosis by angiography in the hospital scale.