An antenna device having a substantially cylindrical shaped case to house the antenna part and a stopper to seal a case opening tightly, wherein the stopper has the first waterproof on the outer periphery to contact the case and the second waterproof on the inner periphery to contact the lead wires. The first waterproof and the second waterproof are disposed on a same location. The present invention can provide the antenna device capable of preventing water immersion into the case simply and reliably without using any filler.