An ultrasonic velocity profile (UVP) method can measure instantaneous one-dimensional velocity profile along the measuring line. It is non-intrusive technique, and it can be easily applied for existing facilities from outside of the test section. Furthermore, the UVP can be used for measuring opaque fluids. The technique was originally developed for use in medical field. Takeda utilized the UVP for measuring in engineering fields in 1986, and it has been widely used for the measurement of the fluid. Now it has been used for many applications such as Taylor-couette flow, liquid metal, multi-phase flow, rheology measurement, flow-rate measurement, and so on.