A mixing element in which spiral blade edge portions are disposed in a tube wall portion of a passage tube through which fluid flows and an opening section of the passage tube and the blade edge portions are joined to each other is provided. In an existing manufacturing method using a gas welding machine, when, for example, a mixing element having an inside diameter of 130 mm is to be manufactured, eight 90-degree rotation type spiral blades can be disposed at most. In a method for manufacturing the mixing element according to the present invention, it is possible to manufacture a mixing element including 10 or more blades by using a laser processor.