There is provided an adjustment circuit which delays a first and a second signal by a desired delay. After the first and the second signal are inputted to the adjustment circuit via a first and a second signal line, respectively, the first and the second signal are exchanged and are inputted via the second and the first signal line, respectively. A detection circuit receives the first and the second signal from the adjustment circuit, and detects the phase differences of these signals, before and after the exchange. The holding circuit holds a first phase difference detected by the detection circuit before the exchange, and holds a second phase difference detected by the detection circuit after the exchange. When the holding circuit holds the first and the second phase difference, a comparison circuit compares these phase differences. A counter counts in accordance with the comparison results of the comparison circuit, and sets the desired delay of the adjustment circuit.