A R-T-B based permanent magnet which has equivalent magnetic properties as the existing Nd—Fe—B based permanent magnet and light mass but also can be suitably used as a magnet for field system of a permanent magnet synchronous rotating machine. The magnet can be obtained in a case where the composition of the compound for forming the main phase is (R1−x(Y1−zCez)x)2T14B (R is rare earth element(s) consisting of one or more elements selected from La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, Y is yttrium, Ce is cerium, T is one or more transition metal elements with Fe or Fe and Co as essential element(s), B is boron, 0.0