A high-frequency surgical PFO closure apparatus used to treat patent foramen ovale in the heart includes first and second electrodes which grasp living tissue of the patent foramen ovale; a high-frequency power supply section which supplies high-frequency power to the living tissue via the electrodes; an impedance measuring section which measures an impedance value by supplying high-frequency power to the living tissue; a grasping condition determining section which determines, based on the measured impedance value, a grasping condition regarding how the living tissue is grasped in blood by the electrodes; and a control section which controls high-frequency power supply at a predetermined power level needed to treat the patent foramen ovale, according to a result of the determination.