Provided is an operation input device for inputting a manipulation command to a manipulator having an end effector for observing or medically treating an affected site. The operation input device includes a grip section that is holdable by changing a method of holding the grip section with the same hand of an operator and an operating section that is provided in the grip section and that is operated with a single finger, which is the same before and after the holding method is changed, so as to manipulate a main function of the end effector.
