To provide a diaphragm breakage detection device for a diaphragm type air pump capable of detecting breakage of a diaphragm in an early stage.

Second discharge passages 12c, 12d to compose the downstream side of a pair of suction/discharge passages are connected to each other to be combined at a position of a communication passage 16 to compose a combined discharge passage, and an unbalance detection means to detect a mutual unbalance condition of discharge pressure of air at the second discharge passages 12c, 12d is provided at a combined connection part. The unbalance detection means is provided with a detection plate 20 supported by one side wall 3a to overhang, and disposed to invade into the communication passage 16 to part a discharge chamber 12 to the right and the left. The detection plate 20 has such a flexiblity to flex toward the low pressure side of discharge pressure of the second discharge passages 12c, 12d. Partition plate folded parts 10a comprising conductive metal to detect flexure conditions of the detection plate 20 by its application to it are provided.