PURPOSE: To mount a lead wires to through holes with good efficiency by a method wherein one side of the lead wire is kept inserted into one side of the through holes, and a pinching body is made to abut to a distance until the interval of the lead wire part becomes the same dimension as the interval of the through holes.

CONSTITUTION: One side of a plurality of lead wires 2 of a DIL type IC is manually inserted into one side of a plurality of the through holes 9 in two rows of a board 8, and next a supporting part 12a on the side of a tool wherein a stopper structure is mounted is made to abut against the outside of the IC lead wire 2 on the side of manual insertion. While, a supporting part 12b on the opposite side of the supporting part of the tool is made to abut against the lead wire 2 on the side of no manual insertion, and the pinching body 11 is made narrow with the side of the supporting part 12b as the fulcrum. When the interval of the through holes becomes equal to that of the lead wire 2, the stopper structure abuts against the inner surface of the pinching body 11; thereby the action toward the inside of the pinching body 11 is regulated.