The present invention relates to a chest expander, wherein the chest expander includes a pair of operating arms that are connected by a rotating shaft to approach or be spaced apart from each other, a plurality of elastic force adjusting holes formed as through holes in a longitudinal direction of the operating arm, elastic members that are disposed between the operating arms to cross and configured to provide an elastic force in a direction in which the operating arms are spaced apart from each other when the operating arms approach each other, and elastic force adjusting parts that allow one end portions of the elastic members to move along the elastic force adjusting holes and to be fixed so that lengths of the elastic members between the operating arms are changed so as to adjust strength levels of the elastic forces of the elastic members.