Threading device of sewing machine

A threading device of sewing machine is disclosed, which is installed in the frame body of sewing machine. The threading device of the sewing machine comprises an elevating/descending unit, and a threading unit. The elevating/descending unit comprises: a driving shaft extending along the direction parallel to the axial line and penetrating the frame body in a moveable and rotational fashion; and a guiding member installed in the driving shaft. The threading unit comprises a threading member having the crochet hook needle part, and a lead thread member. When the guiding member is moved downward by the external force, the threading unit is shifted downward in the linking-up fashion to a horizontal position corresponding to a needle hole of a needle, and further drives the driving shaft to rotate, so as to drive the crochet hook needle part and the lead thread member in the linking-up fashion to rotate opposedly and get close, at the same time, the crochet hook needle part penetrates out of the needle hole. Acco