PURPOSE: To lower the unnecessary radiation level by arranging a coil for cancelling the leak field to be produced from a horizontal deflection coil and a regulator for limiting the power conduction to said cancelling coil.

CONSTITUTION: A cancelling coil 7 has the coil sides 7a, 7b formed along the pass line sections 1c, 1d in front and rear of a horizontal deflection coil 1b with the number of turns about 3W10% of the horizontal deflection coil 1b. Upon supply of horizontal deflection current, leak fields 9a, 9b are produced thus to cancel the leak fields 6a, 6b produced from the pass line sections 1c, 1d of the horizontal deflection coil. A variable coil 8 will regulate the power conduction to the cancelling coil 7 with correspondence to the fluctuation of strength of the leak fields 6a, 6b of a deflection coil 1 thus to minimize the unnecessary radiation level.