The magnetic domain of a Co/Pt thin film that was grown on a crystal (011) Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (PMN–PT) substrate was regulated by an electric field at room temperature (RT). The magnetic hysteresis loops and magnetic domain state were recorded by means of the magnetic optical Kerr effect (MOKE). In the unpoled state, magnetic domain wall propagation was observed directly under a fixed perpendicular magnetic field. In addition, the change of the coercive field under various electric fields was consistent with the change of strain curve—attributed to the piezostrain effect in (Co/Pt)/PMN–PT heterostructure. Moreover, the magnetic domain that was driven by the electric field exhibited a similar behavior. Electric-field control of magnetic domain was demonstrated by exploiting piezostrain-mediated magnetoelectric coupling in ferromagnetic/ferroelectric heterostructures with perpendicular magnetic anisotropy, which is promising for designing of future spin-transfer torque magnetoresistive random access memory devices.