A scan flip-flop includes an input unit and a flip-flop. The input unit is configured to select one signal from among a data input signal and a scan input signal to supply the selected one signal as an internal signal according to an operation mode. The flip-flop os configured to latch the internal signal according to a clock signal. The flip-flop includes a cross coupled structure that includes first and second tri-state inverters which share a first output node and face each other.