To improve economy with a lower price eliminating a retainer by making a looper for bobbin thread function to oscillate itself and pick up a thread.

In a lower shaft looper mechanism 20 of a sewing machine, a pair of collars 24 for pinching is inserted into a looper shaft 23 linked to a retainer shaft arm 22 through which a retainer shaft 21 is inserted while a collar 26 is interposed between a looper shaft spacer 25 of a looper shaft 23 and a looper bracket frame 27. A tapered wedge-shaped tip curved protrusion part is formed on one side of the tip part of a looper 29 for bobbin thread mounted on a looper bracket 28 of the looper bracket frame 27. Thus, a forward action, a right action, a rear action and a left action are performed continuously in sequence in response to a needle bar.