Air tightness testing device

The utility model discloses an air tightness testing device, and belongs to the technical field of air tightness detection equipment. The air tightness testing device comprises an oil cup, a connecting air pipe, an air supply pipe and a connecting clamp used for being connected with a workpiece to be tested in a sealed mode. One end of the air supply pipe is used for being connected with an air supply device, and the other end of the air supply pipe is in sealed connection with the oil cup and extends into liquid in the oil cup; one end of the connecting air pipe is connected with the oil cup in a sealed mode and located above the liquid level of the oil cup, and the other end of the connecting air pipe is connected with the connecting clamp in a sealed mode. According to the utility model, the gas with certain pressure is filled into the closed space of the workpiece to be detected, and whether the oil cup continuously emits bubbles is observed, so that the visual air tightness detection of the workpiece to