Abstract: A jet grouting method is capable of reducing an unnecessary portion (redundant portion) exceeding an effective wall thickness without narrowing a construction pitch, and capable of allowing easy mechanical control. A ground improvement structure including a plurality of ground improvement bodies is constructed through use of the jet grouting method. Each of the ground improvement bodies is constructed so as to have a sectional shape formed by a combination of different kinds of fan shapes having different radiuses. The sectional shape of the ground improvement body is a combination of at least two kinds of fan shapes. One of the kinds of the fan shapes corresponds to a fan shape with a smaller radius, and the other corresponds to a fan shape with a larger radius. The sectional shape of the improvement body has a minimum diameter portion formed of the fan shapes with the smallest radius and a maximum diameter portion formed of the fan shapes with the largest radius.