A single phase motor and a hair dryer are provided. The motor includes a stator and a rotor. The stator includes a stator core and a stator winding. The stator core includes an outer ring portion, teeth extending inwardly from the outer ring portion, and two pole shoes extending from a distal end of each tooth. A winding slot is formed between each two adjacent teeth. A slot opening is disposed between the pole shoes of the adjacent teeth, and is offset from one of the two adjacent teeth. The air supplying unit includes the single phase motor and an impeller. The startup angle and cogging torque of the motor are adjustable by adjusting the position/width of the slot opening, without the need of additional positioning slots or positioning holes defined at the pole shoes, which makes the motor structure simple.