Production of R-Fe-B type permanent magnets has been rapidly increased since its discovery in 1983. This type of permanent magnets is used various applications today. The application for electric motors is one of the expanding field of R-Fe-B magnets in future. We studied the improvement of particular characteristics of R-Fe-B magnets required in motor applicant. In this paper, improvement of high temperature stability, mechanical strength and magnetizability will be reported. By refinement of microstructure, R-Fe-B sintered magnets with high temperature stability comparable to Sm-Co type sintered magnets was obtained. This material also showed high mechanical strength because of its fine microstructure.