A neck joint structure which has an opening on the main face of a body in the thickness direction, which has openings on the side faces of the body extending in the thickness direction, and into which at least a part of the base-end portion of a neck is inserted is formed in the body of a stringed musical instrument. The neck joint structure includes a recessed end face which is brought into contact with the end face of the base-end portion constituting the base of the neck in the longitudinal direction and a recessed bottom face which is brought into contact with the main contact face of thebase-end portion that forms a corner together with the end face in the thickness direction of the neck. The neck joint structure of the stringed musical instrument is equipped with a joint member fixing the body and the neck, i.e. a slanting joint member which is screwed into the body and the neck via the corner between the recessed bottom face and the recessed end face of the body and via the corner between the main contact face and the end face of the neck in the state in which the screwing direction thereof is slanted to the distal end of the neck in the longitudinal direction relative to the thickness direction of the body and the neck.