To provide a steam trap failure detection device which has a simple constitution, is easily mountable and easily-handleable, and simply finds operation failure of a steam trap.

In the steam trap failure detection device 10, a failure of the steam trap 1 is simply known by: fixing one end 18 of a bimetal 12 to the outer wall surface of a steam trap 1 or a steam pipe 2 and a drain pipe 3 connected to the steam trap 1; enlarging a displacement of the tip part of the bimetal 12 displaced by receiving heat by using levers 20, 22; displaying the enlarged displacement of the bimetal 12 through a pointer 42; providing a display board 44 for showing an operation state of the steam trap corresponding to a pointer 42 position; and visually displaying the operation state of the steam trap 1 on a display device 16.