Themagnetic sail is an advanced space propulsion concept that uses an artificial magnetosphere for capturing the solar wind energy. In this study, the interaction of the solar wind with themagnetosphere of a magnetic sail has been simulated based on the resistive magnetohydrodynamics model in two-dimensional space and the plasmadynamic characteristics of magnetic sail were evaluated. When the solar wind is not magnetized by the interplanetary magnetic field, the attitude of the magnetic sail spacecraft is static stable when the magnetic moment vector is perpendicular to the solar wind flow direction. The interplanetary magnetic field not only enhances a drag force in the direction leaving the sun (i.e., thrust) but also acts on the pitching moment; the pitching moment due to the interplanetary magnetic field rotates the magnetic sail spacecraft so as to align the magnetic moment vector parallel to the interplanetarymagnetic field. Despite the weak interplanetarymagnetic field adopted in the simulation, which is 1 order of magnitude lower than the typical value, the pitching moment coefficient is significant. The attitude stability of the magnetic sail is hence strongly affected by the interplanetary magnetic field.