A method of measuring setup time measures a first delay time from an input signal to a clock signal and a second delay time from the clock signal to an output signal, and determines a setup time using the first delay time and the second delay time. The method of measuring setup time is used in designing a semiconductor IC including a pulse-based flip-flop circuit. The semiconductor IC designed by using the method of measuring setup time absorbs a clock jitter and allows a time borrowing between adjacent pipelines.