To enable the high-speed operation of a weaving machine by surely suppressing vibration accompanying with shedding motion and noise accompanying with back and forth vibration of heald frames without being affected by the number of the heald frames.

This vibration-preventing device of the heald frames of the weaving machine prevents the back and forth vibration of the heald frames by arranging plural heald frames between a pair of guide plates installed to be opposed in the back and forth direction of the weaving machine, wherein a pair of stays are laid between the left and right frames of the weaving machine to be separated in back and forth direction, the guide plate is provided for each of the pair of stays, the pair of stays are joined through a joining member with each other, and at least the stay laid in rear direction in the pair of the stays is fixed to the left and right frames so as to be adjusted in the back and forth direction, wherein, the joining member extends in the back and forth direction and in accompanying with the adjustment of the stay, at least one of the joined positions with the pair of the stays is adjusted in the back and forth direction.