The present invention provides a power transmission mechanism. The power transmission mechanism can improve the lowest terrain clearance, ensure the smoothness of the turning and ensure the straight when being assembled to an operation machine. The power transmission mechanism comprises a differential mechanism (40) connected with a first output shaft and a second output shaft and configured to perform drive to absorb rotation difference when the first output shaft and the second output shaft have rotation speed difference; a switching mechanism (60) capable of becoming the allowance state of driving of the differential mechanism (40) when a turning bar (3a) is subjected to turning operation, and when the turning bar (3a) is not subjected to the turning operation, the switching mechanism (60) is switched to the brake state of braking through driving of the differential mechanism (40).