An atomizing unit with a circuitous air passage, including a base, an outer cover, a liquid conducting member, a supporting member, and a heating member. A first air hole and a second air hole communicating with the first air hole are defined in the base; a third air hole is defined in the outer cover; an accommodating cavity is defined in the liquid conducting member and extends through two sides thereof; 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; the supporting member supports the heating member to be attached to an inner side of the liquid conducting member; the groove and the heating member define a ventilation passage communicated with the third air hole; at least a part of the bottom surface of the supporting member and the base define an air space.