An operation instrument includes an electric surgical knife, a fluid ejection surgical knife, and a gripper mechanism. The gripper mechanism including a pair of gripper strips 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 each are provided with an electrode for the electric surgical knife. An ejection opening for the fluid ejection surgical knife is formed in a first gripper strip, and the ejection opening is formed at a position retracted from an end portion on a distal end side of the electrode.
