7²-[2(Z)-ethoxyimino-2-(5-phosphonoamino-1,2,4-thiadiazole-3-yl)acetamido]-3-[4-(1-methyl-4-pyridinio)-2-thiazolylthio]-3-cephem-4-carboxylate, its ester or its salt, which has a superior anti-bacterial activity, stability, absorbability, etc., and a pharmaceutical composition containing it, is provided.