PURPOSE: To easily fix a power semiconductor, etc., tentatively on a printed board without using an exclusive jig by using other electronic components such as resistor and capacitor, which are very common as peripheral electronic components, in place of an aligning member for a power semiconductor, etc.

CONSTITUTION: For mounting an electronic component 3 provided with lead legs such as a power semiconductor, etc., on a printed board 1, other component 5 such as a resistor and capacitor is inserted into an auxiliary board 2, which is formed to be separated from the printed board for alignment, in place of an positioning member. The electronic component provided with lead legs is aligned by using the electronic component 5, the lead legs 4 are inserted into the printed board and after soldering the lead legs to the printed board, the auxiliary board is separated and removed.