To provide a panel mounting adapter capable of easily putting on and off a fluid apparatus including a detecting device such as a sensor, a switch in an operating panel, a controlling system and the like.

A connecting member 18 extending outward in a direction approximately orthogonal to an outer side face 16 of a body 12 is provided in the body 12 formed in an approximately quadrilateral frame body, and a supporting member 24 opposite to the connecting member 18 is arranged therein. The supporting member 24 is firmly fixed to an other side face of a connecting portion 22 formed between a pair of groove portions 34a and 34b in which one end portion is arranged in the frame body of the body 12. The other end portion is extended outward in a direction approximately orthogonal to the outer side face 16 of the body 12 and is bent downward to the connecting member 18. One end portion of a retaining member 26 is held on both sides of the connecting member 18, and the other end portion of the retaining member is extended along an outer side 16 of the body 12 and is bent downward to the supporting member 24. A projection 28 connected with the groove 38 of the connected portion 44 of a pressure switch 40 is formed on one side of the connected portion 22 of the body 12.