Provided is a test method for the detection of diabetic nephropathy at an early stage as compared to a conventional method. Specifically provided are: a test method for diabetic nephropathy, including detecting urinary podocalyxin the test method, further including assessing diabetic nephropathy at at least Stage I a test reagent for use in the test method and a test reagent kit for use in the test method. The present invention is based on a finding that urinary podocalyxin reflects the development and condition of diabetic nephropathy with high sensitivity at an early stage as compared to urinary albumin.
