Turbidity current is generated in an inclined lock-gate flume under a large amount of suspension supply. By opening the gate, turbidity current generates and flows to downstream. The turbidity current maintains its interface structure and progresses with constant frontal velocity. The inner velocity profile of the quasi-steady body by ultrasound velocity profiler (UVP) falls on the similar convex lines within the fluctuations in space and time. We conclude that turbidity current progresses in a steady state flow structure with small dissipation, which is a key to transport a large amount of sediment in a long distance.