We carried out the verification of the piezometric method to observe concerning groundwater flow and solute transport under the unsteady state in the tidal flat. Especially, we considered whether solute moves and reacts instantaneously as pressure head changes in the tidal flat. The results of verification are summarized as follows, (1)The electric conductivity(EC) of water collected from the piezometer changed with the tidal fluctuation, and the variation was similar to that by buried EC sendor. Moreover, the variation accuracy increased by pulling out water in the piezometer just before water sampling. (2)The piezometric head (water table in the pipe) changed with the tidal fluctuation. Especially, it decreased with delaying during falling period of the tide level. This showed that pressure remained under the ground. (3)Our study corresponded to previous studies concerning between the groundwater and solute flux by the piezometric and catchment mass balance methods.Based on these results, we would apply this method to groundwater flow and solute dynamics in the tidal flat.