PURPOSE: To easily disperse and supply the particles of supply raw materials and to accelerate the yield, uniformity and fuel economy of products by fluidizing the supply raw material particles in a reservoir and delivering the particles to a microspheroidization zone under gravity from the opening of an overflow supply port.

CONSTITUTION: The supply raw materials are delivered from a supply device 4 to the microspheroidization zone in a chamber 2 and are heated during the passage along walls 8, 9 having a heater 3 and are converted to glassy beads. These beads are then collected by a collector 6. The supply raw material fed into the reservoir 16 of the supply device 4 in the microspheroidization furnace 1 having the constitution described above are preheated and fluidized by supplying the fluidizing gas heated by a heat exchanger 19 from the porous bottom 17. The fluidized particles are made to flow over a lip 23 and are supplied under gravity from a slit 22 into the heating chamber 2. The supply raw material particles are sufficiently separated by the fluidization and are efficiently heated at a uniform rate in the chamber 2, by which the glassy beads are obtd.