To optimize the ratio of individual inclination angles of an upper inner wall and a lower inner wall to increase the flow speed of the injected air flow from a weft inserting nozzle into a weft-guide groove.

An air jet loom is provided with the weft-guide groove, wherein each inclined reference of each crossing point of the extension of the upper inner wall or lower inner wall with the extension of a back inner wall of the weft-guide groove inclines to the inclined reference of the line perpendicular to the back inner wall, and each of the upper inner wall and the lower inner wall of the weft-guide groove inclines downward to the fabric side, and satisfies the formulas, 8°≤α≤13°, and 12°≤β≤18 wherein, α is the angle of inclination of the upper inner wall, and β is the angle of inclination of the lower inner wall.