Raw material alloy flakes for a rare earth sintered magnet having a roll-cooled surface, obtained by strip casting with a cooling roll having a surface roughness Ra of 2 to 15 μm and a surface roughness Rsk of not less than -0.5 and less than 0, and satisfying requirements to below: said alloy flakes comprise: 27.0 to 33.0 mass% of at least one R selected from the group consisting of rare earth metal elements including yttrium, 0.90 to 1.30 mass% of boron, at least one impurity selected from the group consisting of alkali metal elements, alkaline earth metal elements, and zinc, at a total content of not more than 0.10 mass%, and the balance M selected from the group consisting of transition metal elements, silicon, and carbon, and inevitable impurities, and containing not less than 50 mass% iron as an essential element; said alloy flakes, as observed in a micrograph at a magnification of 100x of its roll-cooled face, have not less than 5 crystals each of which is a dendrite grown radially from a point of crystal nucleation, has an aspect ratio of 0.5 to 1.0 and a grain size of not smaller than 30 μm, and crosses a line segment corresponding to 880 μm; and said alloy flakes, as observed in a micrograph at a magnification of 200× of its section taken generally perpendicularly to its roll-cooled face, have an average distance between R-rich phases, the measurement of which is described in the description on pages 14 - 15, of not less than 1 μm and less than 10 μm. said alloy flakes comprise: 27.0 to 33.0 mass% of at least one R selected from the group consisting of rare earth metal elements including yttrium, 0.90 to 1.30 mass% of boron, at least one impurity selected from the group consisting of alkali metal elements, alkaline earth metal elements, and zinc, at a total content of not more than 0.10 mass%, and the balance M selected from the group consisting of transition metal elements, silicon, and carbon, and inevitable impurities, and containing not less than 50 mass% iron as an essential element; 27.0 to 33.0 mass% of at least one R selected from the group consisting of rare earth metal elements including yttrium, 0.90 to 1.30 mass% of boron, at least one impurity selected from the group consisting of alkali metal elements, alkaline earth metal elements, and zinc, at a total content of not more than 0.10 mass%, and the balance M selected from the group consisting of transition metal elements, silicon, and carbon, and inevitable impurities, and containing not less than 50 mass% iron as an essential element; said alloy flakes, as observed in a micrograph at a magnification of 100x of its roll-cooled face, have not less than 5 crystals each of which is a dendrite grown radially from a point of crystal nucleation, has an aspect ratio of 0.5 to 1.0 and a grain size of not smaller than 30 μm, and crosses a line segment corresponding to 880 μm; and said alloy flakes, as observed in a micrograph at a magnification of 200× of its section taken generally perpendicularly to its roll-cooled face, have an average distance between R-rich phases, the measurement of which is described in the description on pages 14 - 15, of not less than 1 μm and less than 10 μm.