A dental magnetic attachment is a device to retain dental prostheses such as overdentures by magnetic attraction. As compared with mechanical attachments, the dental magnetic attachment has superior characteristics such as easy insertion, good esthetics and less lateral pressure to its abutment tooth. As a result, it has come to be used widely. There are various types of dental magnetic attachments. There are a cup type and a sandwich type in Japan, and several types of dental magnetic attachments in other countries. They are used for a long term in the mouth, it is necessary to clarify those leakage magnetic fields. Therefore, in this paper, we evaluate the leakage magnetic fields leaking out of sandwich type and open magnetic circuit type of dental magnetic attachment.