PURPOSE: To improve quality and productivity of a clinometer, by housing in No.1 fan-like plastic box with an opening of 90°, No.2 box of the same shape in a free- to-rotate position centering in the vicinity of the center section.

CONSTITUTION: In No.1 fan-shape box having a center angle of 90°, No.2 box of the same shape is housed in a free-to-rotate position centering on the vicinity of the center section. Angle scales 3a ranging from 0°W90° are provided on arc-like circumferential surface of the No.2 box and also on arc-like outside circumferential surface, and tip 8a of an indicator 8 is bent at right angle. And therefore, it is possible to observe the scale from both horizontal and vertical directions. On the other hand, on the occasion of assembling of the box 1 and the box 2, the No.2 box is attached to the No.1 box in a free-to-rotate position and placed on the horizontal table, so that it becomes possible to rotate the No.2 box by a screw driver in the manner as indicated by symbols 10 and 10a and to set the indicator 8 to zero. In this way it is possible to improve quality and productivity of the said instrument.