To certainly detect an inclination angle to each turning direction making orthogonal double-axis each other as centers in spite of a simple structure that a liquid dielectric body is sealed in an accommodating container.

A air-tight chamber for accommodating a fluid in which a bottom surface and a ceiling surface are parallel each other is formed in a rectangular and flat accommodating container 2 mounted to an agricultural machinery in a horizontal state. A first and second plane-like electrodes 3a, 3b disposed at a plane symmetric state making an X axis being a lateral axis in the agricultural machinery as a symmetric axis and a third and fourth plane-like electrodes 3c, 3d disposed at a plane symmetric state making a Y axis being a forward/backward axis in the agricultural machinery as a symmetric axis are formed on the bottom surface of the air-tight chamber 2b for accommodating a fluid at an electrically insulated state. A common plane-like electrode 4 is formed on the ceiling surface in a state opposed to the first to fourth plane-like electrodes 3a to 3d. An inclination angle-detecting action is carried out based on a variation of an electrostatic capacity between the plane-like electrodes 3a to 3d and the common plane-like electrode 4. A silicon oil is sealed in the air-tight chamber 2b for accommodating a fluid in a state that a space portion is remained.