Atmospheric pollutant concentrations have been higher around the Osaka Bay and Harima-Nada Sea, and surroundings than those in the other regions of Japan, and is pointed out to be influenced by shipping emissions. The spatio-temporal dynamics of atmospheric SO₂, NO_x, and PM_2.5 were examined based on the ship onboard observations over the Seto inland sea and atmospheric monitoring data. The Conditional Bivariate Probability Function analysis for the Tarumi and Hyogo-nanbu sites showed the air mass inflow with higher SO₂ from the Akashi Strait known as the congested sea area, and that was a different trend from the diurnal NO₂ change characterized with two peaks. Meanwhile the daytime PM_2.5 was increased in the warmer seasons but the diurnal change was lower than the SO₂ and NO_x cases, that implied the long-range PM_2.5 pollution. Ship onboard SO₂ concentrations in the maritime airmass were up to 5 times higher than those at the ground monitoring sites. On the other hand, NO_x and PM_2.5 in the maritime airmass were lower and the same levels when comparing those at the monitoring sites, respectively. These suggested that the major sources of SO₂ and NO_x existed on the sea and on the land areas, respectively.