To provide a treatment method of a treated object capable of implementing continuous treatment as a whole through a process for drying the treated object under reduced pressure, is included.

The treated object D1 supplied through a supply passage 11 is dried under reduced pressure and discharged through a discharge passage 12. Here, the treated objects D1, D2 are continuously supplied and continuously discharged to thicken and material seal the supply passage 11 and the discharge passage 12 by the compressed treated objects D1, D2.