This paper analyzes the effects of port size on port tariff using the data for world major sixteen container ports. Some previous studies show that demand for port services have significant effects on port tariff, but we cannot find studies analyzing the correlation between the supply variables and the port tariff. In this paper, we used the five supply variables, which are the number of gantry crane, the number of berth, the quay length, the terminal area and the storage capacity for containers. The panel regression results are as follows. Port tariff generally decreases as port size increases, which shows that port tariff is explained by the economic theory. However, increase of port size, in some cases, does not reduce port tariffs, which may be due to monopolistic characteristics of port. This paper also shows that both demand and supply factors affect port tariff, but that demand factors have more consistent effect on port tariff than supply factors.