PURPOSE: To measure the two-dimensional or three-dimensional existing position of an object by the measurement from one direction by closely adhering a block having a face orthogonal to the measuring direction and an inclined face to the block.

CONSTITUTION: The upper part 1(Z) of a block 1 has a face P(Z) inclined along Z-axis. The central part 1(Y) has a face P(Y) orthogonal to Y-axis (measuring direction) and the lower part 1(X) has a face P(X) inclined along X-axis. This block 1 has magnetic property, and is closely adhered in a determined position of a work W for use. Each distance measuring sensor SY(Z), SY(Y), SY(X) has a light emitting element and a light receiving element to detect the distance to the respective faces P(Z), P(Y), P(X) with no contact. When this block 1 is mounted on the work W to conduct the measurement from Y-axial direction, not only the Y-axial position but also the X-axial and Y-axial positions can be determined. The work W is carried in X-direction by a carrying line.