A compound or its pharmaceutically acceptable salt represented by the following formula: The invention is a carbapenem compound which has a potent antibacterial activity over a broad range of Gram negative and Gram positive bacteria, especially penicillin-resistant Streptococcus pneumoniae (PRSP) which has been isolated at an elevated frequency in recent years and thus causes a serious clinical problem, and Haemophilus influenzae which has acquired resistance against the existing β-lactam antibiotics over a wide scope due to penicillin-binding protein (PBP) mutations such as β-lactamase non-producing ampicillin-resistant (BLNAR) Haemophilus influenzae, and has excellent oral absorbability.