A synchronous motor, including: an orientation sheet, an orientation gear set, a casing, a rotor, a transmission gear set, an input gear and an output gear set; wherein the orientation sheet is connected with the orientation gear set, and the orientation sheet is provided with a positioning rod, an orientation member and a groove for storing lubricating oil; the bottom surface of the casing is provided with a positioning groove, and the positioning rod is slidably connected with the positioning groove; the rotor is provided inside the casing, the rotor protrudes from the bottom of the casing and is provided with an orientation boss, and the orientation boss bears against the orientation member.