A single-phase brushless motor has both superior start-up stability and low cogging torque. In the outer-rotor-type single-phase brushless motor, when a gap width between the rotor and one edge of the salient pole surface is defined as d1, a gap width between the rotor and the other edge of the salient pole surface is defined as d2, and a minimum gap width between the rotor and the salient pole surface is defined as d3, the formula d3