A new quantitative measurement of tilt and shift mode has been developed to solve the n=1 instabilities of Field-Reversed Configuration (FRCs). The tilt angle and the shift length were measured quantitatively for the first time, using the radial and axial magnetic field components of n=1 toroidal modes, respectively. Our experimental measurement identified for the first time that the prolate FRC inside the cylindrical conducting wall was stable for the n=1 shift mode but unstable for the n=1 tilt mode.