A clutch transmission mechanism of a printing device includes a power input shaft, a power input gear, a gear-shifting arm, a first gear-shifting module and a second gear-shifting module. In the cooperation of these components and modules, the printing device can be operated in a first gear-shifting mode or a second first gear-shifting mode. When the printing device can be operated in a first gear-shifting mode or a second first gear-shifting mode, the clutch transmission mechanism coaxially transmits the driving force. As such, the stability of transmitting the driving force is enhanced.