This book introduces the recent development in Japan of diamond electrodes, which has attracted much attention in the world. For example, electrochemical sensors using diamond electrodes are now being utilized commercially. Newly developing applications such as electrochemical organic synthesis including CO reduction are also expected to form an important future technology. Those emerging applications to various fields which are receiving increasing attention are described in detail here. This book is useful not only for students who would like to begin their study of diamond electrodes but also for industries that are exploring novel electrochemical applications.