Embodiments provide a magnetic memory device and a method of writing a magnetic memory device. The magnetic memory device includes a magnetic tunnel junction including a reference layer, a free layer and a tunnel barrier layer between the reference and free layers, and a first conductive line adjacent to the free layer. A first spin-orbit current having a frequency decreasing with time flows through the first conductive line. The writing method includes applying the first spin-orbit current having the frequency decreasing with time to the first conductive line.