Superconductivity is now a considerable focus of attention as one of the te- nologies which can prevent environmental destruction by allowing energy to be used with high e?ciency. The possibility of practical applications of sup- conductivitydependsonthemaximumcurrentdensitywhichsuperconductors can carry, the value of losses which superconductors consume, the maximum magnetic ?eld strength in which superconductors can be used, etc. These f- tors are directly related to the ?ux pinning of quantized magnetic ?ux lines in superconductors. This book extensively describes related subjects, from the fundamental physics of ?ux pinning to electromagnetic phenomena caused by ?ux pinning events, which will be useful for anyone who wants to understand applied superconductivity. The Japanese edition was published for this purpose in 1994. Since then, there has been signi?cant progress in the research and development of hi- temperature superconductors. In particular, the new superconductor MgB 2 was discovered in 2001, followed by steady improvements in the superc- ducting properties necessary for applications. On the other hand, there are no essential di?erences in the ?ux pinning phenomena between these new superconductors and metallic superconductors. Hence, the framework of the previous Japanese edition was kept unchanged, while new description was added on these new superconductors in the English edition. In the following the content of each chapter is brie?y introduced.