An exemplary atomizer includes a liquid supply, an atomizing head, and an air passage. The liquid supply has a liquid chamber. The atomizing head includes a liquid absorbing element and a heating element. The liquid supply includes a sealing element at an end connected with the atomizing head. The sealing element is configured for sealing the tobacco liquid in the liquid chamber. The sealing element defines a through hole. The liquid supply further includes a magnet configured for sealing the through hole. The magnet abuts against the sealing element via a magnetic force. The atomizing head further includes an electromagnet. The electromagnet is configured for lifting the magnet when powered on, so that the tobacco liquid can flow out from the through hole. The present disclosure also relates to an electronic cigarette.