An axisymmetrical particle-in-cell/Monte Carlo simulation is performed for modeling radio frequency-driven planar magnetron discharge. The model apparatus has a narrow target-anode gap of 20 mm to make the computational time manageable. This resulted in the current densities which are very low compared to actual experimental results for a wider target-anode Sap. The spatial and temporal behaviors of such plasma parameters as plasma density, electric field, and discharge current are examined in detail. The direct current self-bias in the magnetron discharge is first clarified by a numerical simulation. The self-bias arises at the powered electrode due to the axial asymmetry of plasma caused by the magnetic field. The effects of magnetic field strength and secondary electron emission on the plasma parameters and self-bias voltage are also clarified.