1. A control device for weft inserting in a jet loom, comprising: information generating means for detecting a last released timing and a last arrival timing of a weft to be inserted and generating the timing informations corresponding thereto; and control means for obtaining, on the basis of both said timing informations outputted from said information generating means, at least two pieces of operating information selected from a group consisting of the average value of the last released timing, the dispersion of the last released timing, the average value of the last arrival timing and the dispersion of the last arrival timing, and inferring by fuzzy inference a corrected value of either a main pressure or a subpressure for weft inserting so as to make the last arrival timing to be attained at an objective value on the basis of the obtained operating information, and then controlling said corresponding pressure on the basis of the inferred corrected value.