To provide a powder resin coating method and powder resin coating device which can maintain a powder surface as flat irrespective of changes in the average particle size of powder resin. A powder resin coating device (1) includes a powder fluidizing bed (2) storing powder resin, a vibration mechanism (5) connected to the powder fluidizing bed (2), and a control device (8) controlling the frequency of the vibration mechanism (5). The control device (8) includes an average particle size estimation unit (82) that estimates the average particle size of powder resin stored within the powder fluidizing bed (2); an optimum frequency determination unit (83) that determines an optimum frequency for causing the powder surface to flatten based on the average particle size estimated by the average particle size estimation unit (82); and a frequency control unit (84) causing the vibration mechanism (5) to vibrate at the determined optimum frequency.