Two nozzles (37) in pair are provided along an inner circumferential surface (21a) of a concavity (21), air is blown out in a space from a blowout hole (37a) provided at a tip end portion of the nozzle from a side where the nozzle (37) is provided aiming at an opposite side along an inner circumferential surface of the space and a powder contained in the concavity (21) is caused to rise up in the space, whereby the condition of the powder mixed with the air within the space is improved.
