We explain about the method of "Migrating" from Google Earth API to Cesium in this presentation. We have produced digital archives series including "Hiroshima Archive","Nagasaki Archive", "The East Japan Earthquake Archive" and so on using Google Earth API. e.nagasaki.mapping.jp/p/archives-series.html Since Google Earth API to be deprecated at the end of 2015, we had started "Migrating" from Google Earth API to Cesium. The Porting succeeded as a result of the trial and error. Our contents also run on smartphones and tablets as well as on PCs now. We explain know-how and merit / demerit of a shift to Cesium from Google Earth API in this presentation. For example, Basic function of Cesium, the implementation method, the difference between KML and CZML, Supported KML tags, and so on.