Threading device for a sewing machine

The threading device for a sewing machine includes an air inflow shaft 4 having an inlet portion 4d for a gas for receiving a compressed gas, a discharge port 4c 4a to connect to the inlet portion 4d for the gas for discharging the gas and a cylindrical outer surface portion at which the outlet opening 4c opened is; 1e a base portion having a through hole 1a in which the cylindrical outer surface portion is inserted 4a of the air inflow shaft 4 to keep the air inflow shaft 4 in a rotatable manner, and an upper looper-side flow path 1d and a lower looper-side flow path, which are designed for such a connection to the through hole 1a that each may be connected in accordance with a rotational position of the air supply shaft 4 to the outlet 4c.