To provide a method of producing a desiliconized slag rough mineral concentrate which is an inexpensive iron source for obtaining molten iron by being charged with iron ore into a blast-furnace.

The method comprises drying a desiliconized slag coagulated mass so that the moisture content is 5% by mass or less, crushing the resulting desiliconized slag coagulated mass into desiliconized slag grains, sorting desiliconized slag magnetized grains attracted to a magnet from the desiliconized slag grains, and classifying the desiliconized slag magnetized grains so that the mixing ratio of particle size of 5 mm or less is 5% by mass or less.