Abstract: An inner shield made of a magnetic material for shielding the earth magnetism is provided in a color picture tube for preventing the mislanding of the electron beams on phosphor stripes that might otherwise result from the bending of the electron beams caused by the earth magnetism. The inner shield is formed by securing a pair of short side sections and a pair of long side sections to a mask frame such as to define a substantially rectangular space through which the electron beams pass. Gaps offering increased magnetic reluctance are provided between the short side sections on one hand and the long side sections on the other hand, whereby the components of the horizontal earth magnetic field vector are adjusted to cancel electromagnetic forces acting upon the electron beams.