A drill guide jig for guiding a drill orthogonally to a curved surface of a workpiece is disclosed. The jig is provided with a guide member having a guide hole for passing a drill and a holding member for holding the guide member. The holding member has a contact part for making contact with a curved surface of the workpiece on the lower side. The contact part has two contact points for making contact with the curved surface. The two contact points are symmetrical in relation to a center axis orthogonal to a midpoint of a line segment that connects the contact points. The drill is perpendicular in relation to the curved surface of the workpiece because the guide hole is disposed along the center axis.