Abstract: A humidifier includes a water storage tank, a humidification tray, and a drive mechanism. The water storage tank includes a water refilling port, a water supply port, and a water stop valve. The water refilling port is formed to receive water refilling from outside. The water supply port is formed differently from the water refilling port. The water stop valve opens and closes the water supply port. The humidification tray is formed to receive supply of water for humidification from the water storage tank through the water supply port. The drive mechanism stops supply of water from the water storage tank to the humidification tray by driving the water stop valve in accordance with an amount of water in the humidification tray.