The present invention provides antibodies specifically against hDlk-1 and having anti-tumor activity in vivo (anti-hDlk-1 antibodies), a fragments of the antibodies, hybridomas that produce the antibodies, a complex of the antibody or antibody fragment and an agent, a pharmaceutical composition comprising the antibody and the like, a tumor therapeutic agent, a tumor angiogenesis inhibitor, a tumor diagnostic agent, a method for detecting tumor, a kit for detecting and/or diagnosing tumor, etc.