To uniformly soften wax over the entire part regardless of its shape by allowing the exact and easy temperature control in softening the wax.

A softening vessel 3 is formed by superposing first, second and third vessels 3a, 3b and 3c apart spacings disposed therebetween. The first vessel 3a on the outermost side is provided with heaters 4 and is provided with a thermostat 5 which detects the temperature of the first vessel and regulates the temperature in the third vessel to a set temperature. Water is put into the respective vessels to immerse the vessels on the inner side into the water in the vessels on the outer side and the first vessel is heated by the heaters to raise the temperature successively from the outer side to the inner side. The wax W for dental technique put into the third vessel is softened by heating with the hot water in the third vessel.