To provide a control device, control method, and surgical system that can further improve safety. Provided is the control device including: a driving control unit (146) configured to control driving of an arm unit (112) that supports a medical instrument (111); a region setting unit (142) configured to set an intrusion appropriateness region for which appropriateness of intrusion of the medical instrument or the arm unit is determined in a space on a basis of a peripheral image showing a peripheral state of the medical instrument or the arm unit; an intrusion determination unit (144) configured to determine presence/absence of intrusion of the medical instrument or the arm unit into the intrusion appropriateness region when the driving control unit controls driving of the arm unit in accordance with a non-contact operation by a user with respect to the arm unit; and an action instruction unit (145) configured to cause an intrusion hindering action for hindering intrusion of the medical instrument or the arm unit into the intrusion appropriateness region to be executed in accordance with a determination result of the intrusion determination unit.