To provide a device increasing S/N ratio of an optical filler by decreasing optical reflectance of the front surface of a reed dent in an air jet loom, wherein a maintenance device capable of decreasing reflectance of the tunnel circumferential surface of a yarn detecting part of optical fillers by simple operation with a reed fixed on the loom is provided.

The device has a transferring table 3 self-propelling along an upper channel 2 of the reed, a shot container 12 loaded on the upper side of the transferring table, a shot nozzle 10 supported by the transferring table, positioned at the front side of the reed dent and injecting shots in the container to the front side of the reed dent by air jet, and a suction nozzle 11 supported by the transferring table and opposing to the shot nozzle at the back side of the reed dent. Air jet for injecting shots may be supplied from the air source of the loom, and negative pressure for the suction nozzle 11 may be generated by an ejector 32 using air from the air source of the loom.