An object of the present invention is to suppress the increase of coarse particles due to the fusion of powder particles and reduce a ratio of particles that have been excessively spheroidized, when the powder particles are heat-treated. A heat treatment apparatus including a raw-material supply unit, a hot-air supply unit for heat-treating a raw material and a discharge portion for discharging the heat-treated powder particles, and supplying hot air toward a raw material to be supplied from the raw-material supply unit, wherein the hot-air supply unit has a first nozzle and a second nozzle which spread in the radial direction downward from an upstream side in a hot-air supply direction, the second nozzle is arranged in the inside of the first nozzle, the hot air passes through a space between the first nozzle and the second nozzle, and an air-flow adjustment unit section for rotating the supplied hot air spirally along an inner wall face of the apparatus is provided in an outlet portion of the hot-air supply unit.