The antibody of the present invention has an extremely high binding ability to human ZAQL-1, can neutralize the activity of human ZAQL-1, and inhibits the action of human ZAQL-1. Therefore, the antibody is useful as a preventive or therapeutic agent or a diagnostic agent for, e.g., digestive diseases, diseases associated with angiogenesis, diseases relating to pregnancy, eating disorders, sleeping disorders, seasonal depression, reproductive dysfunction, endocrine diseases, senile dementia, Alzheimer's disease, various disorders caused by aging, cerebral circulatory disorders, head trauma, spinal injury, epilepsy, anxiety, depression, manic depression, schizophrenia, alcoholism, Parkinson's disease, hypertension, arteriosclerosis, arrhythmia, premenstral syndrome, glaucoma, cancer, AIDS, diabetes, etc.