To solve a conventional dryer's problems of unequal dryness and reduction of thermal conductivity caused by adhesion of treatment objects to a wall surface of a treatment vessel or conglomerating of the treatment objects in a position where mixing is insufficient, and a problem wherein even scattering objects scattering in the treatment vessel are discharged from an exhaust port and the scattering objects remain in a vacuum pump, in a heat exchanger, etc.

A reduced-pressure dryer 10 heats the treatment objects while mixing them in the treatment vessel 12 having reduced-pressure atmosphere by forcible discharge. In the reduced-pressure drier 10, mixing blades 20 for mixing the treatment objects are composed of: foot parts 29 fixed and installed to a rotation shaft 19; and wing parts 30 attachably/detachably installed to the foot parts 29. The drier is equipped with plate-like members 18 projecting to the radial direction from the rotation shaft 19 of the mixing blades 20.