Abstract: A mode locked fiber laser gyroscope using a rare-earth doped fiber. The mode locked fiber laser gyroscope comprises a fiber amplifying unit, a dichroic mirror connected to one end of the fiber amplifying unit, and a fiber rotation sensing unit connected to the other end of the fiber amplifying unit in order to generate a signal in accordance with rotation of the laser gyroscope. The rare-earth doped fiber constitutes the fiber amplifying unit and is connected at one end thereof to the dichroic mirror and applied with the light of a pumping light source through the dichroic mirror. The other end of the rare-earth doped fiber is connected to the fiber rotation sensing unit. In the mode locked fiber laser gyroscope of this invention, the measurement of a rotation rate from a detect signal of a photo detector does not require a complex signal processing but is directly achieved by a time axis.