An atomizing unit with a circuitous air passage, wherein the atomizing unit comprises: a base, wherein a first air hole is defined in a bottom surface of the base and a second air hole is defined in a top surface thereof, and the first air hole is in communication with the second air hole; an outer cover, wherein the outer cover is arranged on the base, and a third air hole is defined in the outer cover; a liquid conducting member, wherein the liquid conducting member is arranged in the outer cover, and an accommodating cavity extending through two sides of the liquid conducting member is defined in the liquid conducting member; a supporting member, wherein the supporting member is arranged in the accommodating cavity, and a groove is defined in an outer side of the supporting member, and the second air hole faces a bottom surface of the supporting member; and a heating member, wherein the heating member is arranged in the accommodating cavity and located between the liquid conducting member and the supporting member, and the supporting member supports the heating member to be attached to an inner side of the liquid conducting member and the liquid conducting member is configured to conduct liquid to the heating member; the heating member covers the groove of the supporting member such that the groove and the heating member define an ventilation passage, and the ventilation passage is in communication with the third air hole; wherein at least a part of the bottom surface of the supporting member and the base define an air space, and the air space communicates the second air hole with the ventilation passage such that airflow passes through the first air hole, the second air hole, the air space, the ventilation passage and the third air hole in sequence. a base, wherein a first air hole is defined in a bottom surface of the base and a second air hole is defined in a top surface thereof, and the first air hole is in communication with the second air hole; an outer cover, wherein the outer cover is arranged on the base, and a third air hole is defined in the outer cover; a liquid conducting member, wherein the liquid conducting member is arranged in the outer cover, and an accommodating cavity extending through two sides of the liquid conducting member is defined in the liquid conducting member; a supporting member, wherein the supporting member is arranged in the accommodating cavity, and a groove is defined in an outer side of the supporting member, and the second air hole faces a bottom surface of the supporting member; and a heating member, wherein the heating member is arranged in the accommodating cavity and located between the liquid conducting member and the supporting member, and the supporting member supports the heating member to be attached to an inner side of the liquid conducting member and the liquid conducting member is configured to conduct liquid to the heating member; the heating member covers the groove of the supporting member such that the groove and the heating member define an ventilation passage, and the ventilation passage is in communication with the third air hole; wherein at least a part of the bottom surface of the supporting member and the base define an air space, and the air space communicates the second air hole with the ventilation passage such that airflow passes through the first air hole, the second air hole, the air space, the ventilation passage and the third air hole in sequence.