In this paper, I examine the cases of the water commerce between inland Gaul (e.g. Lugdunensis, Aquitania, Belgica, two provinces of Germany, and northern Narbonensis) and Italy. As evidenced by the inscriptions CIL XIII 1942 and VI 29722, two traders engaged in river and marine transportation. It is said that in the first and second century A. D., the nature of the economy of inland Gaul was different from that of the Mediterranean region: indeed, the networks of traders appear to have been divided between those two areas. On the other hand, scholars have often discussed the marine transporters of southern Gaul who were active in the Mediterranean region, some of whom maintained relationships with officers supervising the supply of food in Rome, i.e., the annona. In this case, it should be pointed out that in outlining the plan of the Roman economy, the foregoing studies pay less attention to individual cases. Further, although there is a lack of reliable and detailed evidence, scholars facilely tend to assume that the marine transporters of southern Gaul operated in Italy. Therefore, I focus on the two abovementioned traders who have recorded their own activities in inland Gaul and Italy. CIL XIII 1942 clarifies the fact that the deceased became augustalis both in Lyon and Pozzuoli, having found favor with other augustales, who mainly comprised those engaged in commerce or industry. Further, he had no dealings with the annona or its officials. This allows us to envisage that he had built and developed relationships with a variety of merchants and artisans in both cities by crossing the borders of two different economic blocs. On the other hand, CIL VI 29722 indicates that the deceased participated in commercial activities as a member of a family enterprise based in Lyon and Rome, which had been managed since the generation of his grandfather-a man who had left his mark on both cities. Moreover, it is remarkable that he not only joined more than one trade association based in Lyon or Rome as a member but was also assigned to important posts in the associations. This indicates that using the family enterprise as the first step, he succeeded in building wide human networks beyond associations and regions. In this case too, it is not proved that the deceased had any dealings with the annona. Based on the facts demonstrated above, I conclude that the two traders had wide networks with a variety of merchants or transporters in both inland Gaul and Italy. Further, these traders relied on people of the same social section rather than those from higher sections, such as officers of the state. Moreover, as an aspect of this study, I suggest that the existence of wide-ranging human relationships between the two regions might provide a new perspective on economical structures in the foregoing discussion.