To produce a hollow granular mold flux for continuous casting, having ≤1wt%, desirably ≤0.4wt% moisture content without trouble, such as the lowering of productivity.

Flux raw material is mixed with water to make slurry, and the slurry is atomized by a spray-dryer 2 and granulated to make the hollow granular-state particles 3 having 1.5-5wt.% moisture content. The hollow granular particles are dried to <1wt.% moisture content with a dry-cooling furnace 5 atmospherically shut off with the spray-dryer 2 and after drying, this hollow granular particles are cooled. It is desirable to dry and cool while conveying the hollow granular particles 3 in order with a scrape-out device 6 provided in the inner part of the dry-cooling furnace 5.