To provide a diaphragm breakage detecting device capable of easily detecting breakage of a plurality of diaphragms used as disposed in parallel to generate negative pressure between each other.

This diaphragm breakage detecting device 10 is provided with a negative pressure communication pipe 24 communicated with negative pressure between a plurality of diaphragms 14 and 16, an index member 28 movably disposed in the pipe, and an index member holding part 30 provided in a part of the pipe to hold the index member at a prescribed position by gravity without giving effects of the index member to the negative pressure between the diaphragms. It is also provided with an index member move detecting means 32 to detect move of the index member from the specified position of the index member holding part in the pipe, and an index member move display means 34 to display detection of the move of the index member from the specified position of the index member holding part by the index member move detecting means.