Abstract: An Omnidirectional rain gauge measures an azimuth and zenith direction of flying rainwater. The Omnidirectional rain gauge includes catchment and measurement units. The catchment unit has a plural conical cylinders having individually different heights, and being overlaid so that bottom vertexes of the plural conical cylinders coincide with or come close to each other. The overlaid plural conical cylinders are partitioned by partitions, arranged radially in a plurality of horizontal azimuth directions, to form a plurality of catchment cells. Each of the plurality of partitions is shaped as semicircle following a virtual spherical outer circumference. Diameter of each of top opening parts opposite to the bottom vertexes, of the overlaid plural conical cylinders is sized to follow virtual spherical outer circumference.