PURPOSE: To easily measure the average moisture of a particulate substance in a large volume, by embedding two parallel insulating coating electrodes in the particulate substance having a large volume while measuring electric characteristics between the electrodes.

CONSTITUTION: Electrodes 1, 1' are embedded in a particulate substance at the ends having water-tight covers 4, 4' thereof and the other ends thereof are connected to a measuring instrument 5 to perform measurement. In the electrical equivalent circuit between the electrodes 1, 1', resistors 6, 6' and capacitors 7, 7' are the leak resistances and electrostatic capacities possessed by insulators 2, 2' while a resistor 8 and a capacitor 9 are the leak resistance and electrostatic capacity of the particulate substance. In addition, a resistor 10 coming to a leak resistance value Rx and a capacitor 11 coming to electrostatic capacity Cx are connected to form a circuit and, because the leak resistance value Rx and the electrostatic capacity Cx are values determined by the moisture amount of the particulate substance if the material quality of the particulate substance is determined, if the relation of the preliminarily measured moisture amount and electric characteristics of the particulate substance is calculated, the moisture amount of the particulate substance can be calculated by measuring electric characteristics.