The offensive odor produced from indoor dust accumulated inside a vacuum cleaner is quite unpleasant to the user. In this study, the odor of dust samples prepared under various conditions was examined using an olfactory method that employs the human sense of smell. In addition, the odorous compounds were analyzed by GC-MS. The odor intensity of the dust collected inside the vacuum cleaner increased in proportion to not only the humidity and temperature of the dust, but also to the cleaning period of the container where indoor dust was accumulated. GC/MS confirmed aldehydes to be the main odorous compounds. The dilution ratio at which the stench of the indoor dust was not detected was determined by using the triangle odor bag method.