To provide a highly functional decompression drying machine providing sensuous detailed drying functions such as drying of vegetables or fruits, and using a new heating means for objects to be dried not limited to conductive heat transfer, convection heat transfer, or radiation heat transfer, with both means for normal pressure and decompression in a drying machine internal pressure, and with a plurality of means for stationary, circulating, and exhaust in an air flow in the drying machine, as the detailed drying functions.

The decompression drying machine is composed of a casing capable of enduring decompression, the heating means for heating the objects to be dried such as fruits or fish, and a pressure control means for controlling a pressure in the casing. It is characterized by that a power heat pipe is used for generating an ultrasonic wave of 32.5 kHz when hot water of about 50C is passed through a heat transfer pipe of the heating means, and normal pressure hot air circulation drying can be carried out also.