A brushless DC motor comprising a rotor to which a permanent magnet is attached; and a stator having a plurality of slots, characterized in that: when an effective opening angle of the magnetic pole of said rotor that was set to a predetermined opening angle whose center is a center of a shaft hole of said rotor is θ2 and, a salient area opening angle of the magnetic pole formed within the effective opening angle θ2 of magnetic pole is θ3, and the effective opening angle θ2 of the magnetic pole of said rotor is greater than the salient area opening angle θ3 of the magnetic pole of said rotor with respect to a structural opening angle, the effective opening angle θ2 of the magnetic pole of said rotor is made to be an angle which is not smaller than an electrical angle of 120°, and which is bilaterally symmetrical with respect to a center of a magnetic pole of the permanent magnet, and the effective opening angle θ2 of the magnetic pole of said rotor is formed between both edges at said pole center sides of any two stator teeth (S1 and S4, S2 and S5,..., or S1 and S6, S2 and S7) closest to the electrical angle of 120°, or between both edges at the sides opposite to said pole center sides of any two stator teeth (S1 and S5, S2 and S6,...) closest to the electrical angle of 120, the salient area opening angle θ3 of the magnetic pole of said rotor is made to be an angle which is not larger than the electrical angle of 120 and closest to the electrical angle of 120, and which is bilaterally symmetrical with respect to the center of the magnetic pole of the permanent magnet and is formed between both edges at sides opposite to said pole center sides of any two of stator teeth (S2 and S3, S3 and S4,..., or S3 and S4, S4 and S5,...), or between both edges at said pole center sides of any two of stator teeth (S1 and S5, S2 and S6,...), and a recessed area is provided in said rotor so as to form a gap between said rotor and said stator teeth (S1, S2, S3, S4, S5, S6, S7, S8) wider than a gap between said rotor and said stator teeth (S1, S2, S3, S4, S5, S6, S7, S8) in the salient area opening angle θ3 of the magnetic pole at least in a portion of the effective opening angle θ2 of the magnetic pole beyond the salient area opening angle θ3 of the magnetic pole. when an effective opening angle of the magnetic pole of said rotor that was set to a predetermined opening angle whose center is a center of a shaft hole of said rotor is θ2 and, a salient area opening angle of the magnetic pole formed within the effective opening angle θ2 of magnetic pole is θ3, and the effective opening angle θ2 of the magnetic pole of said rotor is greater than the salient area opening angle θ3 of the magnetic pole of said rotor with respect to a structural opening angle, the effective opening angle θ2 of the magnetic pole of said rotor is made to be an angle which is not smaller than an electrical angle of 120°, and which is bilaterally symmetrical with respect to a center of a magnetic pole of the permanent magnet, and the effective opening angle θ2 of the magnetic pole of said rotor is formed between both edges at said pole center sides of any two stator teeth (S1 and S4, S2 and S5,..., or S1 and S6, S2 and S7) closest to the electrical angle of 120°, or between both edges at the sides opposite to said pole center sides of any two stator teeth (S1 and S5, S2 and S6,...) closest to the electrical angle of 120, the salient area opening angle θ3 of the magnetic pole of said rotor is made to be an angle which is not larger than the electrical angle of 120 and closest to the electrical angle of 120, and which is bilaterally symmetrical with respect to the center of the magnetic pole of the permanent magnet and is formed between both edges at sides opposite to said pole center sides of any two of stator teeth (S2 and S3, S3 and S4,..., or S3 and S4, S4 and S5,...), or between both edges at said pole center sides of any two of stator teeth (S1 and S5, S2 and S6,...), and a recessed area is provided in said rotor so as to form a gap between said rotor and said stator teeth (S1, S2, S3, S4, S5, S6, S7, S8) wider than a gap between said rotor and said stator teeth (S1, S2, S3, S4, S5, S6, S7, S8) in the salient area opening angle θ3 of the magnetic pole at least in a portion of the effective opening angle θ2 of the magnetic pole beyond the salient area opening angle θ3 of the magnetic pole.