In a brushless motor of the present invention, by disposing an electronic circuit board and a rotary magnet close to each other, detection precision of a magnetic pole of a Hall IC is enhanced, and a motor can be reduced in thickness. The electronic circuit board 4 is provided with an opening hole 41 and a notch portion 42 provided on an outer peripheral side of the opening hole 41. A lower insulator 32 of a stator 3 is provided with a positioning surface 32a with respect to the electronic circuit board 4 and an arc projection piece 32c. Portions of coil winding portions of teeth of the stator 3 are fitted into the electronic circuit board 4, a surface of the electronic circuit board 4 is brought into positioning against an positioning surface 32a of the lower insulator 32, and the notch portion 42 of the electronic circuit board 4 and the arc projection piece 32c of the lower insulator 32 are engaged with each other.