The present invention provides a process that treats sludge or incineration ash emitted in greatest quantities and containing a phosphor component and that continuously produces a phosphatic fertilizer and an apparatus therefor. The process that produces a phosphatic fertilizer according to the present invention including the steps of continuously supplying a raw material composed of sludge or incineration ash containing a phosphor component and a reducing agent or a raw material composed of sludge or incineration ash containing the phosphor component, the reducing agent, and at least one of a magnesium component, a calcium component, a potassium component, and calcium-containing waste into a melting furnace which is kept in a reducing atmosphere while an interior of the melting furnace is kept in a sealed state such that the reducing atmosphere is kept in the melting furnace; keeping an inner temperature of the melting furnace at around 1400 °C, heating the raw material while suppressing evaporation of the phosphor component, and causing molten metals and molten slag to coexist in the melting furnace in a two-liquid separated phase; quenching molten slag which flows from the melting furnace; and crushing the quenched molten slag to grains having diameters of 50 µm to 2 mm.