An air jet loom including a sub-nozzle air direction adjustment device, the air jet loom including: a main nozzle for weft insertion; a sub-nozzle for the weft insertion; a reed including a plurality of dents arranged in a weft insertion direction; and a weft passage formed by guide recesses of the dents; wherein a weft yarn to be inserted through the weft passage by air discharged from the main nozzle and the sub-nozzle, the sub-nozzle air direction adjustment device including: a pressure sensor that measures an air pressure of the air discharged from the sub-nozzle at a measurement point group including at least three measurement points, and a display unit that displays the maximum air pressure position (Pc) and a target position (Pt) for the maximum air pressure position (Pc), and displays at least one of a movement path (Tp) of the maximum air pressure position (Pc) obtained by rotating the sub-nozzle in a circumferential direction with an axis of the sub-nozzle at a center, and a movement path (Tt) of the target position (Pt), the movement path (Tp) of the maximum air pressure position (Pc) and the movement path (Tt) of the target position (Pt) being on the imaginary plane including the measurement point group; characterized in that the sub-nozzle air direction adjustment device further includes: a calculation unit that calculates a maximum air pressure position (Pc) that is positioned on an imaginary plane including the measurement point group and where the air pressure of the air discharged from the sub-nozzle becomes maximum, based on measured values at the measurement point group measured by the pressure sensor. a main nozzle for weft insertion; a sub-nozzle for the weft insertion; a reed including a plurality of dents arranged in a weft insertion direction; and a weft passage formed by guide recesses of the dents; wherein a weft yarn to be inserted through the weft passage by air discharged from the main nozzle and the sub-nozzle, the sub-nozzle air direction adjustment device including: a pressure sensor that measures an air pressure of the air discharged from the sub-nozzle at a measurement point group including at least three measurement points, and a display unit that displays the maximum air pressure position (Pc) and a target position (Pt) for the maximum air pressure position (Pc), and displays at least one of a movement path (Tp) of the maximum air pressure position (Pc) obtained by rotating the sub-nozzle in a circumferential direction with an axis of the sub-nozzle at a center, and a movement path (Tt) of the target position (Pt), the movement path (Tp) of the maximum air pressure position (Pc) and the movement path (Tt) of the target position (Pt) being on the imaginary plane including the measurement point group; characterized in that a pressure sensor that measures an air pressure of the air discharged from the sub-nozzle at a measurement point group including at least three measurement points, and a display unit that displays the maximum air pressure position (Pc) and a target position (Pt) for the maximum air pressure position (Pc), and displays at least one of a movement path (Tp) of the maximum air pressure position (Pc) obtained by rotating the sub-nozzle in a circumferential direction with an axis of the sub-nozzle at a center, and a movement path (Tt) of the target position (Pt), the movement path (Tp) of the maximum air pressure position (Pc) and the movement path (Tt) of the target position (Pt) being on the imaginary plane including the measurement point group; the sub-nozzle air direction adjustment device further includes: a calculation unit that calculates a maximum air pressure position (Pc) that is positioned on an imaginary plane including the measurement point group and where the air pressure of the air discharged from the sub-nozzle becomes maximum, based on measured values at the measurement point group measured by the pressure sensor.