PURPOSE: To easily implement focus adjustment implemented in response to a change in a picture size by adding a DC bias compensating a change in a lowermost point of a parabolic wave amplitude to a static focus voltage.

CONSTITUTION: An earth side terminal 21 of a voltage division circuit being a component of a static focus voltage generating means 9 of a flyback transformer 20 is connected to a DC bias generating means 19. A DC bias generating means 19 is driven by a signal in response to a horizontal size of a picture from a horizontal size control means 15. Then a DC bias to compensate a change at a lowermost point caused by a change in a parabolic wave amplitude obtained from the DC bias generating means 19 is added to the static focus voltage. Then the static focus voltage with the DC bias added thereto and a parabolic wave voltage whose amplitude is adjusted by the parabolic wave amplitude adjustment means 13 are superimposed and the result is applied to a focus electrode 7 of a cathode ray tube 6.