An exposure apparatus for exposing a phosphor screen of a cathode ray tube includes a light source portion having an elongate light source lamp and a shading member arranged to face the lamp. The shading member is formed with a slit through which a light beam from the lamp passes. The slit is formed in a V-shaped configuration in which it protrudes toward the light source lamp. The shading member is formed such that a cross section thereof in the direction in parallel to the axis of the light source lamp has a wedge-like shape in which the thickness increases from the edge of the slit toward the end thereof in the direction of the axis, and such that a cross section in a direction perpendicular to the axis has a uniform thickness at the position of the slit.