PURPOSE: To detect only a true angle of inclination without the influence of force applied with an inclinometer inclined through the simple constitution by coupling a float and weight together by a coupling member and by positioning the fulcrum where the coupling member is supported in the center of the whole moment of interia.

CONSTITUTION: Hollow ball 1 made of a nonmagnetic matrial is filled with liquid 2. In ball 1, hemispheric hollow float 3 and hemispheric weight 5, for example, are coupled together by coupling member 4 and supported by supporting member 7 at their crossing point 6. Supporting member 7 is fixed to ball 1 and coupling member 4 is capable of rotating freely on fulcrum 6 in three axial directions. Over the surface of float 3, magnet sheet 8 is provided and on the external surface of ball 1, magnetic resistor 9 detecting its intensity of magnetism is also provided, thereby measuring the angle of inclination by the resistance variation of magnetic resistor 9 due to variation in opposite area 10 according to the angle of inclination. Since fulcrum 6 is set in the center of the whole moment of interia, the true angle of inclination is measured without any influence of force applied in inclination and the constitution is simple.