The indoor air quality management of the public places is gaining wide attention in Korea, because theindoor air quality of the public places are obliged to satisfy the guidelines suggested by Korean Ministryof Environment. According to this regulation, the railroad stations are regarded as public places whilethe passenger cabin of train is excluded. However, because the passengers spend more time in thepassenger cabin than in the stations, the indoor air quality management of the passenger cabin is moreimportant. Recently, Korean government prepares a new law which is regulating the indoor air quality ofthe railroad passenger cabin. In this study, the indoor air quality of the high-speed train passengercabin in Korea was investigated to prepare the appropriate guidelines for the passenger cabin. Thetemperature, relative humidity, particulate matter concentration, carbon monoxide concentration,carbon dioxide concentration, formaldehyde concentration, and volatile organic compoundconcentration were measured during the running of the train with passengers. The carbon dioxideconcentration was measured to largely exceed the normal indoor air quality guideline level, 1,000 ppm(particle per million). Therefore, the appropriate countermeasure to reduce the carbon dioxideconcentration is required. In case of particulate matter, PM-10 concentration was measured to bemostly lower than normal indoor air quality guideline level, 150 ?g/m3. However, the PM-10 leveldrastically increased when the train stopped at the stations. So, it could be concluded the managementof particulate matters in stations is one of the most important factors for the control of the indoor aircabin passenger cabin. Volatile organic compound and formaldehyde concentrations were measuredas 56.08 ppb and 6.49 ppb, respectively. We suggested several ways to improve the indoor air qualityof the railroad passenger cabin as a conclusion.