To provide an apparatus and a method for generating ozone where the generating efficiency of ozone is certainly enhanced.

The apparatus for generating ozone 1 has a cylindrical internal electrode 2, an external electrode 3, a discharge space 6 and a solenoid exciting coil 5 to generate a magnetic field along an axis direction. The width dr of the discharge space 6 is at least the maximum width of the circulating motion of electrons in the discharge space 6 which is decided by (i) the maximum value of magnetic flux density produced in the discharge space 6 by the solenoid exciting coil 5 and (ii) the maximum value of an electric field produced in the discharge space 6.