Disclosed is a method and an apparatus for soldering a base material. A binary solder essentially consisting of tin and a metal which can form an eutectic alloy with tin and which is exclusive of lead is prepared. The content of other metallic components is 0.1% by weight or less and the content of oxygen is 100 ppm or less. The binary solder is melted in a non-oxidizing environment and dispensed to the base material in an atmosphere in which the oxygen content is 2,000 ppm or less, to solder the base material with the binary solder. The soldering apparatus comprises an oscillator for supplying oscillatory wave energy having frequency of 15 KHz to 1 MHz to the base material. The soldering apparatus can also be realized in the form of a soldering nozzle or a soldering iron.