As a development of the equation obtained in the 1st Report, the pressed-out (or drawn-in) flow through a channel of rectangular cross-section (Fig.1) has been studied to see the effect of trapping flow in a gear pump on the pump power and discharge. (1) Work done for trapping flow is composed of two parts, one being that to overcome friction, which is rather small, in order of 1/20 of the total friction loss of power, and the other that to overcome the pressure at the opening. (2) The dividing wall, in the relief groove, between the delivery and suction sides has the optimum thickness for the increase of discharge, depending upon the resistance of the groove. Fig.8. shows the volumetric efficiency, which is defined as η_ν=ΔV/V, where ΔV=volume of fluid delivered to the pressure side and V=volume of fluid pressed out by the trapping action.