An optical fiber grating part including an elongated pedestal, and a base plate installed on said pedestal, and having a different coefficient of linear thermal expansion from said pedestal, and an optical fiber passing through said pedestal, and connected to connection points installed on said pedestal or said base plate located apart from each other in the longitudinal direction of said pedestal, and having an optical fiber grating located between said connection points, wherein a predetermined tensile force is added to said optical fiber grating, and said pedestal and said base plates thermally expand or thermally shrink independently in the longitudinal direction of said pedestal, and an extension line of an axis of said optical fiber joining said connection points passes through a contact surface between said pedestal and said base plate.