Recently, the semiconductor processing technology is advancing. The development of the semiconductor technology influences in fields other than electronics. With the development of this technology, A lot of Microdevice has been proposed. In a chemical field and the medical treatment field, etc the research of a minute space has been attracted. In this research, The flow of the passage where width is one millimeter was measured. The measuring method used resistance CT. The sample used ferrofluid. The density distribution of ferrofluid was measured by resistance CT method and The image of making to visible was restructured based on the data.