In the present invention, a surgical system has: a power supply device that is provided with first signal and second signal generation units that respectively generate a first signal and a second signal as high-frequency signals; a surgical treatment tool which is provided with a converter that converts a supplied second signal to other energy, and a pair of electrodes; a cable which connects the surgical treatment tool to the power supply device; a measurement unit which measures a high-frequency voltage and a high-frequency current with respect to biological tissue to which a high-frequency signal is supplied via the cable and the surgical treatment tool; a calculation unit which calculates capacitive values of the cable and the surgical treatment tool on the basis of the measured high-frequency voltage and high-frequency current; an assessment unit which assesses whether or not the calculated capacitive values are smaller than a threshold for detecting disconnection; and a control unit which performs output control of the high-frequency signals and the like on the basis of the assessment results by the assessment unit.