This is a series of researches which aim to make fundamentally clear the effects of the bulk plastic deformation of work metals on the frictional mechanism at tool-work interface. In the first report, the contact ratio R and the frictional shear stress τf are measured on metal surface of blank-holder side in the sheet metal drawing and U-bending of strips. The bulk plastic deformation occurs together with the frictional sliding in the former, but does not occur in the latter. By comparison of the results in both cases, the effects of the bulk plastic deformation on R and τf can be examined. The following have been concluded. (1) The values of R in the case of the sheet metal drawing are 2.5∼3 times greater than those in the case of the U-bending. This is due to bulk plastic deformation. (2) Within the limits of this experiment, the frictional shear stress τf is approximately proportional to the real contact pressure, irrespective of presence of the bulk plastic deformation.