Electromagnetism is an important subject in today’s physics. The number of textbooks on electromagnetism is much larger than those on other subjects. This is because abstract concepts are frequently used and therefore it is not easy for students to come to a complete understanding of electromagnetism, although variousphenomenaareconciselydescribedwithmathematics.Forthisreasonmany textbooks have been published to assist students to understand electromagnetism better. Why, then, is a new textbookon electromagnetismnecessary now? Electromagnetismisaclassicalsubjectthatwasalmostcompletelyformulatedin the nineteenthcentury.However,concerningits theoreticaldescription,there is still roomforfurtherprogress.Inaddition,textbooksarerequiredtodescribetheirtopics adequatelywithin a limited space. Therefore,there is also roomforimprovementin textbooksfrom the technical point of view.