To facilitate threading to a looper and to improve the efficiency for threading work.

The looper threading device 1 is for threading to thread holes 21 and 31 formed in loopers 2 and 3 which oscillate to form seams. The looper threading device 1 comprises threading members 8a and 8b formed to hold threads at the distal ends and to be inserted into the thread holes, guide members 7a and 7b for movably storing the threading members and guiding the threading members to the thread holes, and a moving mechanism 60 for moving the guide members and the threading members to the thread holes disposed on the moving paths of the threading members so that the distal ends of the threading members pierce through the thread holes. Each threading member comprises a shaft part 8g or 8h formed long along the direction of movement and a plurality of bristle-like parts 8m or 8n formed on the surface of the shaft part.