An anti-sloshing moon pool structure is disclosed. The anti-sloshing moon pool structure of the present invention includes moon pool plates (112, 114 and 116), which are provided on a bow-side wall (401), a stern-side wall (403) and opposite sidewalls (405) of a moon pool (100), and a moon pool bottom block (130), which is provided on a bow-side lower edge (407) of the moon pool (100). The moon pool plates and the moon pool bottom block have protruding lengths within which they do not interfere with a maximum working area. Upper steps (112a, 112b, 114a, 114b, 116a, 116a-1, 116b and 116b-1) of the moon pool plates are disposed such that, when a ship is in a working position, they are lower than the free surface of the seawater, and lower steps (112c, 112d, 116c and 116d) of the moon pool plates are disposed such that, when the ship runs, they are lower than the free surface of the seawater.