A vehicle-mounted air purifier 1 includes a main unit incorporating an ion generator. The main unit is removably arranged within a passenger space inside a vehicle. For example, if a beverage container holder 90 is provided inside the vehicle, the main unit can be removably arranged within the passenger space when given a cylindrical shape that permits it to be held in the beverage container 90. The power from which the vehicle-mounted air purifier 1 operates can be taken from a cigarette lighter power outlet 91 provided inside the vehicle through a connection cable 92. The main unit is thus arranged directly within the passenger space, and the ions generated by the ion generator inside are fed into the passenger space with higher efficiency. The main unit is removably arranged as an independent unit. Thus, even when the ion generator breaks down or otherwise its replacement becomes necessary, the arranged ion generator can be removed readily and replaced easily.