• Patients who undergo kidney biopsy and are diagnosed as having idiopathic membranous nephropathy prior to the obtainment of informed consent

• Patients who are diagnosed as having nephrotic syndrome prior to the obtainment of informed consent and receive no steroids or immunosuppressants within 12 weeks prior to the obtainment of informed consent

• Patients with urine protein-creatinine ratio ≥ 3.5 g/gCr at the screening

• Patients with hypoalbuminemia (serum albumin ≤ 3.0 g/dL) at the screening

• Patients aged 15 years or older at informed consent

• Patients who give voluntary written consent after having received adequate information on this study (legally acceptable representatives should also give consent for underage patients, and informed assent should be obtained from children)