PURPOSE: To produce material particles which can give a resin foam in which a powder is uniformly distributed, by melt-extruding a foaming resin material into a rod, attaching a powder to the rod before solidification, solidifying it by cooling and dividing it into granules.

CONSTITUTION: A resin material (e.g., polystyrene) is molten by heating in a heater 2 and the resulting resin melt is extruded through a number of fine holes of an extruder 3. While it is being transferred in the direction of an arrow, it is solidified by cooling with air supplied into a cooling apparatus 8 to form a rod-like material 7. On the other hand, a powder 4 (e.g., cement powder) is blown from a supply device 5 against the above rod-like material 7 in a state after extrusion by the extruder 3 and before complete solidification to attach the powder uniformly to the surface of the rod-like material 7. After the powder- attached rod-like material is solidified completely, it is divided into granules by means of a granulator 12 and sent to a receiver 13.