PURPOSE: To accurately detect the position of an air bubble, by enclosing a conductive fluid in a hermetically sealed insulating container so that a predetermined air bubble is formed, and electrically detecting as well as displaying the position of the air bubble.

CONSTITUTION: A plurality of electrodes 2a, 2b, 2c are disposed so as to emerge into the inside of an insulating container 1 made of glass or the like. The ends of the respective electrodes are made flush with the inner wall of the insulating container 1. A conductive fluid is enclosed in the insulating container 1 so that an air bubble 4 having a predetermined volume is formed, and the container 1 is hermetically sealed. In case of utilizing the air bubble detector thus constructed as an attitude gyro, the horizontality degree of an object can be readily detected from the lighting state of each of light-emitting diodes 203, 205, since the electric resistance between the electrodes changes with the horizontality degree of the object.