A new method is developed to measure rainfall with high accuracy and resolution. The principle of new method is to detect a weight change of a buoyant weight according to a change in water level of raingage measured by the use of a strain-gage load cell. Field test of the method was carried out on 30 September 1998, when there was heavy rainfall with total amount of 189.60mm. The results are as follows; 1) In spite of heavy rainfall, this new method showed the total error of only 1.5% against the total amount of 189.60mm. 2) This new mechanism accomplished high accuracy and resolution at filed test in heavy rainy day. 3) The present study provided a possibility to develop a new raingage with an 0.01mm in rainfall measurement.