The present invention relates to a pharmaceutical composition for preventing or treating a fracture or osteoporosis, including, as an active ingredient, a gene selected from a group consisting of slit1, slit2, slit3, robo1, robo2 and vilse, or an expressed protein of the gene. The present invention also relates to a marker composition for predicting the risk of the occurrence of a fracture or osteoporosis, the marker composition including the protein, to a kit for predicting the risk of the occurrence of a fracture or osteoporosis, the kit including an antibody that specifically binds to the protein, and to an information provision method for predicting the risk of the occurrence of a fracture or osteoporosis, including the step of measuring the level of expression of the slit protein through an antigen-antibody binding reaction using an antibody that specifically binds to the protein. The slit3 of the present invention may increase bone formation and decrease bone reabsorption in a cellular and animal model, and has a negative correlation with the incidence rate of osteoporosis. Therefore, it can be used effectively as a composition for preventing or treating a fracture or osteoporosis and as a bio marker for prediction of the risk of the occurrence of a fracture or osteoporosis.
