An operation instrument (10) includes an electric surgical knife, a fluid ejection surgical knife, and a gripper mechanism (52). The gripper mechanism including a pair of gripper strips (53, 54) configured to be openable and closable so as to grip a living tissue and at least one of which is a movable portion. The gripper strips (53, 54) each are provided with an electrode (110) for the electric surgical knife. An ejection opening (212) for the fluid ejection surgical knife is formed in a first gripper strip (53), and the ejection opening is formed at a position (53b) retracted from an end portion on a distal end side of the electrode.
