There is a need for a new antibiotic having a novel mechanism of action, which exhibits strong antibacterial activity not only against sensitive bacteria, but also against resistant bacteria thereof, and at the same time possess excellent solubility and safety profile amenable to human use. As a result of intensive research, the present inventors have found that N-phosphonoxymethyl prodrugs of hydroxyalkyl thiadiazole derivatives represented by general formula (I), a regioisomer, a stereoisomer, or a pharmaceutically acceptable salt thereof possess excellent solubility and safety profile for use in human for the treatment of bacterial infectious diseases.