The invention provides a manufacturing method of an R-T-B sintered 
magnet. By adopting the method, a heavy 
rare earth element RH diffuses inwards from the surface of R-T-B sintered 
magnet raw materials without lowering the residula 
magnetic flux density, and the fracturing and damages of the R-T-B sintered 
magnet are inhibited. The manufacturing method comprises an R-T-B sintered magnet 
raw material preparing step, an RH 
diffusion source preparing step, a step for loading the R-T-B sintered magnet raw materials, RH 
diffusion sources and stirring auxiliary parts in a 
processing chamber; and an RH 
diffusion step for moving the R-T-B sintered magnet raw materials, the RH diffusion sources and stirring auxiliary parts and simultaneously heating the R-T-B sintered magnet raw materials and the RH diffusion sources. The size of each R-T-B sintered magnet 
raw material is larger than 1000mm3, and the 
maximum size is two times of the minimum size among the sizes in three orthotropic directions. Each RH diffusion source is smaller than 3 mm. The stirring auxiliary parts include a plurality of first ball bodies and a plurality of second ball bodies.