The purpose of our study is to know the interaction between a flow and a surface of hydro gel. Tissue of living organ like blood vessel, cartilage and eyeball is a hydro gel. It contains water, so that the surface of hydro gel is considered to be water. Thus, it is a hydrophilic material. We expect it to show good reduction of friction if we use it the wall of a conduit. To check the concept, we measured velocity profile of a film flow on the hydro gel by a micro PIV method, estimating wall share stress from the velocity gradient at the wall. We confirmed slip-velocity depending on degree of swelling of hydro gel and the flow inside of gel induced by shear stress.