A 60-year-old man presented with nephrotic syndrome (NS). Light microscopy of renal biopsy specimens showed minor glomerular abnormalities, while immunofluorescence microscopy revealed solitary polyclonal granular IgA deposition along the glomerular capillary walls. Electron microscopy showed small amounts of electron-dense deposits in the subepithelial area, but not in the mesangial area. In this patient, apparent underlying disease was not found during the 3-year follow-up, and low-dose prednisolone was effective in the treatment of NS. To our knowledge, there is only one case report of membranous nephropathy with clinicopathological features similar to our case.