A fiber optic bio-sniffer (biochemical gas sensor) for alcohol gas monitoring with high sensitivity and high selectivity was fabricated and tested. The bio-sniffer is a gas sensor that uses molecular recognition of enzyme to improve selectivity. Usually, enzyme loses activity in the gas phase. Applying a flow-cell with a gas-intake window to the sensing probe, enzyme immobilized at the sensing region was kept in the sufficient wet condition to maintain activity. The bio-sniffer measures ethanol (EtOH) vapor by measuring fluorescence of nicotinamide adenine dinucleotide (NADH), which is produced by enzymatic reaction at the flow-cell. In order to construct a simplified system suitable for on-site applications, a high-intensity ultraviolet light emitting diode (UV-LED) was utilized as an excitation light. Owing to low power consumption comparing with previous light sources, the bio-sniffer was considered to be suitable for laptop applications such as on-site monitoring. According to the characterization, the bio-sniffer for was useful for continuous alcohol monitoring and showed high selectivity. The calibration range was 0.30-300 ppm which is suitable for evaluation of capacity to metabolize alcohol.