The present invention relates to an electric motor comprising a casing on which a plurality of heat dissipating fins extending in a longitudinally direction are disposed along a circumferential direction to form a longitudinally extending cooling airflow passage between adjacent heat dissipating fins; a first end cap and a second end cap attached to the casing at the ends to form a substantially closed interior space; a rotating shaft rotatably supported by the first end cap and the second end cap; a rotor positioned within in the internal space and mounted to the rotating shaft; and a stator positioned within in the internal space, surrounding the rotor and disposed adjacent to the casing. The electric motor further comprises an airflow guiding device disposed on the heat dissipating fins and allowing the heat dissipating fins to expose partially to the surrounding environment in the circumferential direction of the casing, the airflow guiding device is configured to divert the cooling airflow that tends to escape from the cooling airflow passages to the surrounding environment in the middle of the cooling airflow passages back into the cooling airflow passages. According to the present invention, it is possible to cool evenly the electric motor and improve the heat dissipation efficiency.