Compounds having potent antimicrobial effects over Gram-positive bacteria and Gram-negative bacteria, a high stability to .beta.-lactamases and DHP-I and a high safety for the human body and a process for producing the same. Carbapenem compounds represented by the following general formula (I) or salts thereof: ##STR1## wherein the ring A represents a 3- to 7-membered non-aromatic ring containing at least one nitrogen atom and optionally having a substituent other than R.sup.6 ; R.sup.1 represents hydrogen or methyl; R.sup.2 and R.sup.5 are the same or different and each represents hydrogen or a protecting group of the hydroxyl group; R.sup.3 represents hydrogen or a protecting group of the carboxyl group; R.sup.4 represents hydrogen, lower alkyl or a protecting group of the amino group; R.sup.6 represents: (1) hydrogen, (2) lower alkyl, optionally substituted by an optionally protected hydroxy, carbamoyl, formimidoyl, acetimidoyl or ##STR2## wherein R.sup.7 and R.sup.8 are the same or different and each represents hydrogen, lower alkyl, or a protecting group of the amino group), or (3) a protecting group of the amino group or a protecting group of the imino group; and m is 0 or 1. These compounds have antimicrobial effects and are useful as a drug.