An adjustable axial-flux disc motor, that is used in a flat space formed at a side or at the center of a wheel center for driving the wheel to rotate. The motor is activated to perform a rotation movement by the interactions of an electromagnetic field formed from the passing of an electric current through the armatures of its stator and a magnetic field resulting from the permanent magnet of its rotator. Moreover, there is a circular air gap sandwiched between the stator base and the rotator base, and the permanent magnet is further surrounded by coils. By adjusting the excitation current of the coils, the magnetic flux intensity can be modulated accordingly, and as the air gap magnetic flux is varied with the relative positioning of the stator and the rotator, the output characteristic of the motor will be varied accordingly.