The drying characteristics of porous materials immersed in a superheated steam fluidized bed tinder reduced pressure were examined. The effect of pressure in the drying chamber on the drying characteristics was compared with that of hot air fluidized bed drying. The sample temperature in drying is almost equal to the boiling point of water in the case of superheated steam fluidized bed drying, and the temperature is higher than that in the case of hot air fluidized bed drying. The sample temperature becomes lower its the pressure in the drying chamber decreases, since the boiling point of water decreases. The effect of the mass velocity of the drying gas is not significant when the fluidization state is sufficiently vigorous. As the pressure in the drying chamber decreases, the difference of drying characteristics between superheated steam fluidized bed drying and hot air fluidized bed drying becomes small.