The present invention relates to a vehicular atmosphere purifying apparatus and has the purpose of providing a vehicular atmosphere purifying apparatus such that the deterioration in performance of an ozone purifier can be diagnosed with a less expensive configuration. In a routine shown in FIG. 12 when it is determined that there is a deterioration diagnosis request the amount of moisture that has already accumulated in ozone purifying sites of activated charcoal at the time of the request is calculated (step 210). When the amount of accumulated moisture is not less than a predetermined amount it is determined whether the state is such that the amount of desorbed moisture can be calculated (step 230). When it is determined that the amount of desorbed moisture can be calculated the amount of desorbed moisture is calculated (step 240) and the calculated amount of desorbed moisture is compared with a deterioration determination value (step 250). When the amount of desorbed moisture is less than the deterioration determination value it is determined that the activated charcoal is deteriorated and an MIL (62) is turned on (step 260).
