A surgical operation system 1 includes a US signal output section 50, an HV signal output section 60, a monopolar type probe 8 having a treatment section 9 which has an HV signal applied thereto and vibrates by ultrasound, a counter electrode plate 3 that forms a return circuit of the HV signal, an HV signal main control section 61c that performs feedback control of the HV signal output section 60 based on the HV signal, a US signal main control section 51 c that performs feedback control of the US signal output section based on a US signal, and an HV signal auxiliary control section 51b that controls the HV signal output section 60 based on the US signal, and has a response time shorter than that of the HV signal main control section 61 c.
