PURPOSE: To increase a drying rate and to obtain a low moisture content by using a dryer as a concentrator as a pretreatment for drying and adding a spray type superheated steam dryer which utilizes superheated steam.

CONSTITUTION: The steam of high temp. and high pressure which is compressed with a steam compressor 8 is fed to a steam condenser 7 provided in a heating drum 1 to heat and concentrate the material 3 to be dried, which sticks to the outside surface of the drum 1, in a constant drying region. Concd. cake 16 is transferred by a transfer pump 17 for concd. cake to a superheated steam dryer 29, where the material is sprayed from spray nozzle 18. Since the superheated steam 23 which is superheated by a boiler 24 is circulated by a blower 25 at a specified velocity in the dryer 29, the cake 16 spryaed from the nozzle 18 is heated to dry cake. Thus, the drying rate is increased and a low moisture content is obtained.