PURPOSE: To provide a duty-cycle control apparatus wherein an internal control clock in each functional block at the inside of an LSI chip can be controlled precisely and, consequently, the precise duty-cycle dependence of each functional block inside the LSI chip can be measured.

CONSTITUTION: An input-clock generation device 2 generates an input clock to an LSI chip 7. An internal-control-clock dutycycle detection device 5 detects the duty cycle of an internal control clock which is output to the outside from a monitoring pad 9 on the LSI chip 7. A duty-cycle correction device 6 controls the input-clock generation device 2 on the basis of an expected value from a clock-duty-cycle expected-value setting device 1 and on the basis of a detection result by the internal-control-clock duty-cycle detection device 5. Thereby, the duty cycle of the input clock is corrected.