To provide a gradient rule which is smaller than a conventional rule and can measure a gradient safely, accurately and easily even in a bad foothold.

This gradient rule comprises a measuring member 10 which has an abutting surface 11 abutting to a face 2 to be measured, and a horizontal reference member 20 which is supported pivotally to the measuring member 10 by a turning center shaft 30 being in parallel with the abutting surface 11 and has a level 26 detecting the level in a plane perpendicular to at least the turning center shaft 30. The turning angle of the measuring member 10 to the horizontal plane 1 is measured as the gradient of the face 2 to be measured by turning the horizontal reference member 20 by using the level 26 such that the horizontal reference member 20 is in parallel with a horizontal plane 1 in a state that the abutting surface 11 is abutted to the face 2 to be measured.