[en] We carried out aerial radiation monitoring (ARM) of all Japan area in order to investigate the influence of the radio cesium which was emitted into the atmosphere by disaster of the Fukushima Dai-ichi nuclear power plant of Tokyo Electric Power Co., Inc. AMS can measure a gamma ray quickly by flight from 300 m height above the ground. Moreover, ARM has an advantage which can grasp self-possessed quantity distribution of an air dose rate and radioactive cesium in ^field^, and is visually intelligible. Although there were apparatus and the technique of ARM in our country, sufficient preparations for wide area monitoring were not made. Therefore, it fixed based on the method of the U.S. Department of Energy (DOE) about the method of the conversion to all radiation dose, and the conversion method to radiocesium deposition and the method of mapping. It is possible to discriminate from a background (cosmic-ray, self-contamination and natural nuclides) at the time of western-part-of-Japan measurement by improving of the method in parallel to data acquisition. By this monitoring, it was able to check about the distribution situation of the air dose rate of the Japanese whole region, or the radioactive cesium deposition. Here, the measurement technique and a result are described. (author)