The test condition for presuming vehicle indoor VOC concentration from the VOC measured value from the parts obtained from the chamber method was examined. As a result of evaluating the influence of solar radiation, the conditions with solar radiation were understood that about 4% of solar radiation loading dose is high as compared with solar-radiation-less conditions. Moreover, . for which the VOC emission factor(diffusion speed) from parts found that the influence of an air change rate(ventilation rate) was great, as a result in order to carry out vehicle indoor VOC prediction realization from a chamber method more, it is required to measure by the air supplying amount of a real vehicle.