To simultaneously detect the inclined angle and inclined direction of an object to be inspected in multiple directions, by computing the angle and the direction based on each paired detect signals outputted from each pair of light receiving elements of a plurality of pairs of light receiving elements arranged on the same circumference in oppositely faced states.

Light receiving elements D1, D2, D3, and D4 arranged facing oppositely on the same circumference respectively output desired detecting signals (a), (c), (b), and (d) in accordance with the quantities of light rays made incident on the elements D1, D2, D3 and D4 from an LED 9 through a liquid 19. Electric signals A and B are respectively generated from two sets of the detecting signals (a) and (b), and (c) and (d), and inputted to an electric signal inputting means 21A. The arithmetic means 21B of an inclination information detecting means 21 computes and outputs an angle detecting signal C as the electric signal corresponding to the inclined angle of a housing 3 and a direction detecting signal D as the electric signal corresponding to the inclined direction of the housing 3 based on the two sets of electric signals A and B. Therefore, the inclined angle and inclined direction of an object to be detected attached with an inclination sensor 1 can be detected simultaneously in multiple directions.