The mechanism of the pressure rise in a gas-liquid two-phase pipe flow of magnetic fluid under a nonuniform magnetic field is investigated in detail both theoretically and experimentally. First, governing equations of one-dimensional gas-liquid two-phase magnetic fluid flow are presented and numerically solved. Next, the pressure distribution in a nonuniform magnetic field region is measured in the cases of two-phase flow, single-phase flow and the stationary state using a new experimental apparatus for the flow system. From the numerical and measurement results, the magnitude of the pressure components which contribute to the total driving force is accurately estimated. These results on the pressure distribution will contribute to the development of the new energy conversion system using a gas-liquid two-phase magnetic fluid flow.