An apparatus includes plural combinations of a clock supplier and a clock supply destination supplied with a clock from the clock supplier. The clock supply destination includes a return route through which the clock supply destination returns a clock to a corresponding clock supplier. The clock supplier includes a variable delay unit that adds a delay to the clock to be supplied to a corresponding clock supply destination; a comparison-reference-clock supply unit that supplies a comparison reference clock having the same phase as that of a comparison reference clock supplied from other clock supplier; a phase comparator that compares the phase of a return clock returned from a corresponding clock supply destination with that of the comparison reference clock; and a phase-difference control unit that controls the delay, so that the phases of the return clock and the comparison reference clock coincide with each other, based on the comparison result.