Air tightness testing device

The utility model is suitable for the technical field of testing, and provides an air tightness testing device which comprises an air supply assembly, a pipeline assembly and a testing assembly. The pipeline assembly comprises a first pipeline, a second pipeline and a third pipeline; the first end of the first pipeline is connected with the air outlet end of the air supply assembly, and the second pipeline is connected with the second end of the first pipeline and used for connecting a to-be-tested piece; the third pipeline is connected with the second end of the first pipeline or is configured to be connected with a to-be-tested piece; the testing assembly comprises a pressure gauge, the pressure gauge is provided with a first air hole communicated with the third pipeline and a second air hole communicated with the outside, and the first air hole and the second air hole are formed in the two opposite ends of the pressure gauge respectively; the pressure meter is configured to obtain pressure values through t