A soil improvement material comprising a ground burned product A and gypsum, the burned product A having a hydraulic modulus (H.M.) of 1.8 to 2.3, a silica modulus (S.M.) of 1.3 to 2.3, and an iron modulus (I.M.) of 1.3 to 2.8. The soil improvement material is useful for improving the ground, especially through solidifying soft soil, such as water-rich soil or organic-rich soil.