Solder bath and method of heating solder contained in the solder bath

A method of heating solder contained in a solder bath, the method comprising the steps of:

• heating a heating element that is buried in a porous heat insulator, said heating element being mounted on outer surfaces of a bottom and sides of the solder bath main body and being away from a thermal diffusion member that is made of stainless steel, said thermal diffusion member being mounted on outer surfaces of a bottom and sides of the solder bath main body;
• heating the thermal diffusion member by heat of the heating element to heat the solder bath main body evenly through thermal diffusion from the thermal diffusion member up to a constant range of temperature;
• and
• heating the solder contained in the solder bath evenly by the solder bath main body heated to the constant range of temperature.