To provide an operating state detection device for a valve, configured to allow a sensor for detecting operating state to be easily attached to a part to be detected.

An operating state detection device 2 includes: an operating state detection sensor 3 which is brought into contact with an entrance 1 of a steam trap which is a part to be detected; a holding member 4 which has an upper wall, both sidewalls, and a substantially U-shaped cross section, in which the operating state detection sensor 3 is connected to the upper wall, a pair of insertion holes is formed, and a notched part communicating with one of the insertion holes and used for inserting one of the legs 6a of a U-bolt 6, is provided on the upper wall or one of both sidewalls; the U-bolt 6 with legs 6a inserted into the pair of insertion holes in the holding member 4; a pair of nuts 7 attached to both legs of the U-bolt 6; a washer 8 having a substantially U-shaped cross section and inserted into one of the legs 6a of the U-bolt 6 which is inserted into one of the insertion holes which communicates with the notched part; and a flat washer 8 inserted into the other leg 6a of the U-bolt 6 which is inserted into the other insertion hole.