Ejection-period setting method for sub-nozzles in air jet loom

An ejection-period setting method for sub-nozzles (21) in an air jet loom is provided. The sub-nozzles (21) are divided into groups (1G to 13G) of sub-nozzles (21) that are connected to a common electromagnetic on-off valve (36). The groups (1G to 13G) are divided into downstream and upstream group sets (GU1 and GU3) which each include two or more groups and an intermediate group set (GU2) including the remaining groups. Ejection-amount reducing patterns (patterns hereinafter) are determined and stored in advance in an arbitrarily selectable state, each pattern being determined by setting an ejection-period reducing mode for each of subject group sets in units of predetermined periods so that each pattern includes the ejection-period reducing modes for all of the subject group sets, the subject group sets including the intermediate and upstream group sets (GU2 and GU3). In a process of setting the ejection periods of the sub-nozzles (21), ejection end times of the ejection periods are corrected when a pattern is selected by an operator.