A body structure of a stringed instrument is designed to reduce weight and to improve sound quality with respect to a solid body, which is constituted by a core material and a pair of decorative boards, wherein the core material is composed of a single material having a relatively low specific gravity (e.g., 0.4 or less) such as falcata, bass wood, and balsa, while the decorative boards each have hardness greater than that of the core material. The core material has curved flatness (or curvature) in which both sides lying in the width thereof are reduced in thickness compared with the center portion thereof. The core material having a relatively low specific gravity is sandwiched between the hard decorative boards; hence, it is possible to reduce the overall weight while securing satisfactory strength.