At least two pairs of auxiliary coils are disposed externally on a deflection yoke at positions which are symmetric with respect to the central axis of a horizontal direction of said deflection yoke and which are separated from each other in the direction of the axis of a cathode ray tube. At least two pairs of auxiliary coils are respectively disposed in front of and at the back of the longitudinal center of a magnetic core. The auxiliary coils have a horizontal length which is longer than its another length. A horizontal deflecting current is supplied to the first pair of auxiliary coils in the direction in which unnecessary radiant magnetic fields generated in front of and at the back of the deflection yoke are suppressed, and a horizontal deflecting current is supplied to the second pair of auxiliary coils in the direction in which an unnecessary radiant magnetic field generated at the back of the deflection yoke is intensified. In consequence, unnecessary radiation can be suppressed simultaneously in front of and at the back of the deflection yoke by a correction apparatus which has a simple structure and which requires no large space.