This paper focused on the evaluation of thermal comfort in 1,000 ton patrol vessel using PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied). Environmental factors, room temperature and relative humidity, was measured in various cabins. Human factors, clothing and activity, in the vessel were modified using inland indoor characteristics and investigated by the survey research for maritime polices. Most crews were satisfied with thermal environment in wheel house and accommodation 1. However, in galley, engine control room. engine room and auxiliary machine room, the number of crews who is not satisfied with the environment was increased remarkably. The most sensitive factor to PMV is room temperature in wheel house and accommodation where crews do a light work and metabolic rate in galley, engine control room and etc. where they do a hard work. Therefore, it is necessary to operate a HVAC (heating, ventilation and cooling) system controlled by proper thermal factors in each cabin. This operating system would be one of the economic and comfortable design techniques that the whole cabins are maintainable the ideal thermal comfort conditions.