An air purifier is provided which can effectively purify the air for a long period of time without increasing the capacity of an internal power supply and an external power supply. A control section determines, by means of a power supply detection circuit, whether or not the external power supplies power. The control section causes an ion generator drive circuit and a fan motor drive circuit to perform operations in accordance with the determination. For example, the control section causes the ion generator drive circuit and the fan motor drive circuit to perform continuous operation in a case where the external power supply supplies power, and causes them to perform intermittent operation in a case where the external power supply does not supply power.
