PURPOSE: To change detection sensitivity according to its optimum detection range by obtaining the split-wound coil of an optical fiber coil and then turning over the coil partially.

CONSTITUTION: An optical fiber coil 3 is not wound collectively but is wound for a plurality of times. For example, a series of optical fibers are wound in a first split-wound coil 3a and a second split-wound coil 3b (both in clockwise twining) and the upper split-wound coil 3b is removed from the coil 3a and is reversed. With the double split configuration, by setting the split ratio of coil to 3:1, the coil 3b where the total optical fiber length is 1/4 is in clockwise twining on reversal and generates sagnac effect in the opposite direction from the coil 3a, thus enabling the detection sensitivity of an angular velocity to be 1/2.