An atomizer, comprising: a shell defining a smoke outlet, a liquid cavity and an atomizing chamber, wherein the liquid cavity is capable of storing a fluid to be vaporized, the smoke outlet communicates with environment outside of the shell; and a heating assembly separating the smoke outlet and the liquid cavity from the atomizing chamber, and comprising a liquid guiding member, a cover, a heating component and a sealing component engaged between the cover and the liquid guiding member; wherein the cover is an integral structure defining a liquid tunnel and a smoke tunnel, the liquid tunnel communicates with the liquid cavity and extends to the first surface of the liquid guiding member, the cover defines an accommodating space, an opening of the accommodating space faces towards the liquid guiding member, and the liquid guiding member is partially received in the accommodating space, the cover covers the first surface of the liquid guiding member and one portion of the second surface of the liquid guiding member, another portion of the second surface of the liquid guiding member is exposed in the atomizing chamber; the liquid guiding member is configured to transport the fluid from the liquid tunnel to the atomizing chamber, and to heat the fluid to generate smoke in the atomizing chamber; the smoke outlet communicates with the atomizing chamber via the smoke tunnel, such that the generated smoke is allowed to exit from the smoke tunnel and further enter the smoke outlet; the heating component is connected with the liquid guiding member, and is configured to heat the liquid guiding member; and the sealing component defines a through hole extending from the liquid tunnel to the first surface of the liquid guiding member. a shell defining a smoke outlet, a liquid cavity and an atomizing chamber, wherein the liquid cavity is capable of storing a fluid to be vaporized, the smoke outlet communicates with environment outside of the shell; and a heating assembly separating the smoke outlet and the liquid cavity from the atomizing chamber, and comprising a liquid guiding member, a cover, a heating component and a sealing component engaged between the cover and the liquid guiding member; wherein the cover is an integral structure defining a liquid tunnel and a smoke tunnel, the liquid tunnel communicates with the liquid cavity and extends to the first surface of the liquid guiding member, the cover defines an accommodating space, an opening of the accommodating space faces towards the liquid guiding member, and the liquid guiding member is partially received in the accommodating space, the cover covers the first surface of the liquid guiding member and one portion of the second surface of the liquid guiding member, another portion of the second surface of the liquid guiding member is exposed in the atomizing chamber; the liquid guiding member is configured to transport the fluid from the liquid tunnel to the atomizing chamber, and to heat the fluid to generate smoke in the atomizing chamber; the smoke outlet communicates with the atomizing chamber via the smoke tunnel, such that the generated smoke is allowed to exit from the smoke tunnel and further enter the smoke outlet; the heating component is connected with the liquid guiding member, and is configured to heat the liquid guiding member; and the sealing component defines a through hole extending from the liquid tunnel to the first surface of the liquid guiding member.