An atomizing device of an electronic cigarette is disclosed. The atomizing device comprises a liquid cup used for accommodating tobacco liquid, an outer tube wrapped outside the liquid cup and a heating atomizing component disposed at a bottom of the liquid cup. A bottom of the heating atomizing component is sealed by a liquid blocking plug. A top of the liquid cup is provided and disposed with a detachable top cover and a detachable sealing plug used to seal the top of the liquid cup. A liquid filling hole and an exhaust hole are respectively disposed and installed at the liquid cup. The atomizing device of an electronic cigarette of the present invention is able to avoid any difficulty of pouring tobacco liquid due to incapability of exhausting air resided in the liquid cup out, and to accelerate a pouring speed of tobacco liquid so that production efficiency is enhanced.
