An automated column-switching liquid chromatographic– atmospheric pressure chemical ionization–mass spectrometric (LC–APCI-MS) method for the simultaneous determination of frequently encountered benzodiazepine hypnotics and their relevant metabolites in urine has been established. A column-switching online solid-phase extraction technique was employed to enhance sensitivity and eliminate tedious sample pretreatment. The combination of an N-vinylacetamide-containing hydrophilic polymer online extraction column and a C18 semi-micro LC column provided the successful separations and MS determinations of the 11 benzodiazepines and 11 relevant metabolites tested in this study. The detection limits ranged 2–10 ng/mL and 10–50 ng/mL in the SIM and full-scan modes, respectively, using 50 µL of urine. The calibration curves were linear up to 500 ng/mL for all these analytes in the SIM mode. The present method provided successful forensic applications for the proof of benzodiazepine administration.