Abstract: In a method for continuously burning particles in a gas or oil heated vertical furnace in which the particles are charged from an uppermost part of the space, and the particles bed fluidized by a burning gas flow is formed in a vertically successive downward arrangement and then the burned particles are discharged out of the bottom of the furnace after cooling, the improvement comprises the steps of: providing the furnace with a plurality of downwardly vertically successive zone, including a precipitation zone of the particles at an uppermost part in the furnace, a lower upward flow velocity zone having low upward stream of the burning gas (referred to as "rich fluidized bed", hereinafter) and a higher upward flow velocity zone having high upward stream of the burning gas (referred to as "lean fluidized bed", hereinafter) underneath the precipitation zone wherein the lean fluidized bed is formed beneath and adjacent to the rich fluidized zone, and feeding the particles, burning them successively through the z