An atomizing device includes an atomizing sleeve, an air pipe received in the atomizing sleeve, an annular space being formed between the air pipe and the atomizing sleeve for containing a tobacco oil, an oil obstructing ring located at an end of the air pipe, the oil obstructing ring having an oil hole, an atomizing assembly positioned under the oil obstructing ring, a screw sleeve and an electrode respectively electrically connected to the atomizing assembly; and a flexible membrane having an inner wall attached to the electrode, and an outer wall in contact with an inner wall of the screw sleeve. The flexible membrane is capable of deformable to form an air space between the outer wall of the flexible membrane and the inner wall of the screw sleeve. An electronic cigarette using the atomizing device is also provided.