A method for producing an RFeB system sintered magnet with the main phase grains having a grain size of 1 μm or less with a considerably equal grain size, including: preparing a shaped body oriented by a magnetic field and sintering the shaped body, wherein the shaped body is prepared using an alloy powder of an RFeB material having a particle size distribution with an average value of 1 μm or less in terms of a circle-equivalent diameter determined from a microscope image, the alloy powder obtained by pulverizing coarse particles having fine crystal grain, each coarse particle having grains of the RFeB material formed inside, the crystal grains having a crystal grain size distribution with an average value of 1 μm or less in terms of the circle-equivalent diameter determined from a microscope image, and 90% by area or more of the crystal grains being separated from each other.