In a method of measurement of the birefringence of an optical fiber, the round-trip Jones matrix R(z) for a first interval (0, z) from a measurement starting point 0 in the optical fiber for measurement to a prescribed position z, and the round-trip Jones matrix R(z+.DELTA.z) for a second interval (0, z+.DELTA.z) from the measurement starting point 0 to a position z+.DELTA.z differing from the position z, are acquired, the eigenvalues .rho..sub.1, .rho..sub.2 of the matrix R(z+.DELTA.z)R(z).sup.-1 are determined, and by computing the following equations (1) and (2),.PHI..function..rho..rho..DELTA..times..times..lamda..PHI..times..pi.- .DELTA..times..times. ##EQU00001## (where .phi. represents the phase difference between linear polarization components due to birefringence, .DELTA.n represents birefringence, and .lamda. represents wavelength), the birefringence in the infinitesimal interval .DELTA.z from the position z to the position z+.DELTA.z is obtained.