A fluid-supplying/discharging system for use in medical devices includes a supplying/discharging device and a tubular-path-resistance changing mechanism. The supplying/discharging device includes a pump capable of supplying and discharging fluid, a tubular path having two ends, connected at one end to the pump and at the other end to a medical device, and a control device connected to the pump and configured to control the supplying and discharging of the fluid to and from the pump. The tubular-path-resistance changing mechanism changes resistance to the fluid flowing through the tubular path.