A powder supply apparatus, comprising a powder receiving device which receives powder, a hopper for storing powder that has an outlet at the bottom thereof, a screw feeder which is provided at the outlet of the hopper, has an extrusion port, and pushes the powder received from the outlet of the hopper toward the extrusion port by a screw. The powder supply apparatus also has a diaphragm pump having a suction port and a discharge port, and discharges air sucked from the suction port to the discharge port by an operation of a diaphragm. An atmospheric passage communicates the suction port of the diaphragm pump with the atmosphere. A communicating passage communicates the discharge port of the diaphragm pump with the powder receiving device. The extrusion port of the screw feeder is positioned within the atmospheric passage so as to supply the powder to the atmospheric passage.
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