PURPOSE: To enable the leads of a surface-mounting type LSI package to be well soldered.

CONSTITUTION: A dip soldering device 1 is equipped with a holder 9 which enables a horizontally held LSI package 7 to move up or down and to rotate at a high speed and an overflow tank 4 provided with a solder outlet 6 which is located confronting the lead 11 of the horizontally held LSI package 7. When the leads 11 of the LSI package 7 are coated with solder, the leads 11 are dipped into molten solder 2 as the LSI package 7 is held horizontal by the holder 9, thereafter the LSI package 7 is made to rotate horizontally at a high speed to separate and remove excessive molten solder deposited on the leads 11 by a centrifugal force.