The breaking limit of multi-directional random waves is still unknown and is requested to be formulated numerically from coastal and ocean engineering viewpoint. In this paper, a breaking wave gauge is newly devised to measure the wave breaking inception as accurately as possible. Indoor laboratory experiments have shown that the breaking wave gauge is able to measure the breaking inception and that the breaking limit of multi-directional random waves becomes smaller than that of the regular wave. The critical wave steepness of multi-directional random waves is revealed to become smaller as the spreading parameter Smax increases.