Method of operating phase change memory device

An operation method of a phase change memory device is provided to prevent overheat of a phase change layer during a reset action, thereby improving durability of the phase change memory device. A phase change memory device comprises a phase change layer and a voltage applying unit. A reset voltage(Vreset) is applied to the phase change layer. The reset voltage comprises first to third pulse voltages(V1~V3). Strength of the first to third pulse voltages is the same. Application time(T1~T3) of the first to third pulse voltages is less than 20ns. An interval between the first and second pulse voltages and an interval between the second and third pulse voltages are less than 100ns. After the reset voltage is applied, a set voltage is applied to the phase change layer.