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PROBLEM TO BE SOLVED : To provide a sintered permanent magnet exhibiting a high oil resistance which has a corrosion resistance and has a function of a barrier against hydrogen even in a high-temperature and high-pressure atmosphere of coolant and lubricant easily and at a low cost. SOLUTION : An alloy which contains R (R is Nd or a combination of Nd and one or two types of other rare-earth elements or more), T (T is Fe or Fe and Co) and B in major proportions and has 17-33.5 wt.% of Nd, 26.8-33.5 wt.% in total of R, 0.78-1.25 wt.% of B, 0.05-3.5 wt.% of the total amount of one or two types of elements chosen from Ni, Ga, Zr, Nb, Hf, Ta, Mn, Sn, Mo, Zn, Pb, Sb, Al, Si, V, Cr, Ti, Cu, Ca and Mg, and the remainder of wt.% of T and inevitable impurities is cast and is ground in an oxygen-free atmosphere of argon, nitrogen or vacuum. Then operations of fine grinding, molding in the magnetic field, sintering and aging are performed in sequence to form a sintered magnet.