To provide an air-injection unit in a loom, capable of automatically adjusting exhaust-staring timing according to changed quantity in air-injection timing or open-close timing, while the air-injection unit is so structured that residual air remaining in air supply pipelines is exhausted after completion of air injection from nozzles.

In this air-injection unit 1 (picking motion of the air jet loom), electromagnetic on-off valves 13, 23 and electromagnetic exhaust valves 14, 24 are each mounted on the air supply pipelines 12, 22 for connecting a pressurized air source 11 and the nozzles (a main nozzle 10 or sub-nozzles 18), the open-close timing (open timing Bs and close timing Be) for the electromagnetic on-off valves 13, 23 and exhaust timing (the exhaust-starting timing Cs and exhaust-ending timing Ce) for the electromagnetic exhaust valves 14, 24 are independently set, and the exhaust timing (the exhaust-starting timing Cs and the exhaust-ending timing Ce) of the electromagnetic exhaust valves 14, 24 is adjusted according the changed quantity in the open-close timing when the open-close timing (the open timing Bs and the close timing Be) of the electromagnetic on-off valves 13, 23 is changed.