The turbidity maximum (TM) is a special region where the maximum concentrations of suspended particulate material (SPM) occur relative to SPM concentrations both upstream and downstream of an estuary. Therefore, SPM concentrations show a specific distribution in an estuary. Published observations of SPM concentrations within a short, weakly tidal, and microtidal estuary are not sufficient. We investigated longitudinal and vertical distributions of SPM and salinity at spring and neap tides in the weakly mixed, microtidal MIYAKO river estuary. The maximum concentration of SPM in the water column of the tidal area occurred at a constant distance from the mouth of the MIYAKO river estuary at ebb tide. The phenomena of the maximum concentration of SPM in the water column of a tidal area do not correspond to the definition of TM. The distance of the maximum concentration of SPM from the river mouth is not affected by tidal range. The maximum concentration of SPM in the water column of a tidal area increases with tidal range. The order of the maximum concentration of SPM in the MIYAKO river estuary is comparable to that in other microtidal estuaries. We presumed the export of SPM in the MIYAKO river estuary is comparable to that in other microtidal estuaries We presumed the export of SPM in the MIYAKO river from our own investigated data.