A positioning device and a positioning method thereof are provided. The positioning device can cooperate with a first satellite group and a second satellite group, and it comprises a storage, a receiver and a processor. The receiver is configured to receive a first satellite group signal from the first satellite group and a second satellite group signal from the second satellite group. The processor is electrically connected to the storage and the receiver, and configured to calculate a positioning offset value according to one of the first satellite group signal and the second satellite group signal. In addition, the processor is configured to calculate a positioning result according to the second satellite group signal and the positioning offset, and store the positioning result in the storage.