To provide an apparatus for controlling a weft running direction in an air jet loom capable of preventing the raging of weft Y and enabling the stable weft inserting.

A fixed air guide 10 is placed between a main nozzle MN and a guiding groove R3 for a reed R. The air guide 10 has air guiding surfaces 11 above and below the swinging loci at the front and rear sides of the main nozzle MN, and the diffusion of the air from the main nozzle MN is prevented by the air guiding surfaces 11 with the result that the running direction of weft Y is correctly controlled.