To provide an operating state detection device for a valve which enables an operating state detection sensor to be easily mounted on a detecting portion.

An operating state detection device 2 includes: an operating state detection sensor 3 abutting on an inlet 1 of a steam trap being a part to be detected; a holding member 4 to which the operating state detection sensor 3 is connected and which has a pair of insertion holes and is positioned at one surface of the inlet 1 of the steam trap; a clamping member 5 which is positioned at the opposite surface of the inlet 1 of the steam trap, formed approximately in a channel shape in cross section having an upper wall and both sidewalls, and having a pair of insertion holes in the upper wall, a plane part which is formed between a pair of the insertion holes, contacts with the plane part of a square pillar of the detecting portion and grooves of approximately dog let shapes in cross section that are formed on both sidewalls, and contacts with both sides of the curved surface of a round pillar of the detecting portion; a U bolt 6 both legs 6a which are inserted into a pair of the insertion holes of the clamping member 5 and a pair of the insertion holes of the holding member 4; and a pair of nuts 7 screwed to both legs 6a of the U bolt 6.