A speaker diaphragm includes a base material impregnated with a thermosetting resin composition. includes the step of subjecting the component in an impregnating step to an impregnating thermo-hardening agent, and thereafter in a curing step placing the component in a curing bath for curing the impregnating thermo-hardening agent present within the component. The exciting light is radiated out from an outside surface of the sensor section in order to excite a fluorescent substance for indicating the presence of a substance to be analyzed in the liquid sample. A main cutting edge is formed at an intersection between the first side surface and the top surface. Each of these steps may be performed wholly from the inside of the stomach and thus can eliminate the need for any surgical or laparoscopic intervention.