PURPOSE: To simply align a long pin with the long pin guide hole of a front head within a short time to insert the same in the guide hole.

CONSTITUTION: In a jig for assembling a dot impact printing head of two-stage constitution consisting of a front head equipped with short pins 14 and a rear head equipped with a long pin, an introducing groove 71 in which a plurality of the short pins 14 and the long pin 24 are inserted so as to be pulled out, a quide 7 having a plurality of the positioning grooves provided to one side edge of the introducing groove 71 at a predetermined pitch and the spacers 8 inserted in the introducing groove 71 of the guide 71 to close the positioning grooves 72 are provided.