PURPOSE: To remarkably increase the quantity of an ore to be charged, and also to elevate its yield and quality, by executing compression of a charging material layer and groove-piercing of the material layer, when converting a powder iron ore to a lump by a sintering machine.

CONSTITUTION: A material 13 charged onto a pallel 1 of a DL sintering machine is compressed by a holding plate 14 or a roll, etc., and density of the charged material is raised. Subsequently, in this material layer 13, a groove-piercing jig 16 is fixed and installed by a supporting base 17. In this state, as the layer 13 moves in the direction as indicated with an arrow together with the pallet 1, a thin groove is pierced in the layer 13 the jig 16. The jig 16 is installed at a constant interval in the width direction of the pallet 1, and one row or more are installed in the direction being in parallel with width of the pallet, and its interval, width, thickness, angle, depth, etc. are selected suitably depending on a material to be used and the working condition. In this way, as for a sintered ore 2 on a fire grate 5, a combustion melting zone 3 and an unfired material 4, becomes good in its permeability owing to the thin groove 7, therefore, productivity of the sintered ore can be secured, and an advancing speed of the melting zone 3 can be equalized.