Fibrous basic magnesium sulfate particles are continuously produced by the process comprising the following steps: (1) placing in a reaction vessel a seed particle-containing aqueous dispersion comprising fibrous basic magnesium sulfate seed particles dispersed in an aqueous medium; (2) supplying magnesium hydroxide and magnesium sulfate continuously into the reaction vessel under heating and stirring the seed particle-containing aqueous dispersion, whereby depositing basic magnesium sulfate produced by the reaction between the magnesium sulfate and magnesium hydroxide in the presence of water on the surfaces of the fibrous basic magnesium sulfate seed particles, to give an aqueous dispersion containing an increased amount of fibrous basic magnesium sulfate particles; (3) taking the aqueous dispersion obtained in the step (2) continuously out of the reaction vessel; and (4) recovering fibrous basic magnesium sulfate particles from the aqueous dispersion taken out of the reaction vessel.