A surface exposure device for use in a copying apparatus essentially comprising a supporting surface for supporting thereon an original from which a duplicate is desired, a lens assembly, a first carriage having therein a reflective mirror and a second carriage having therein at least one reflective mirror. The first and second carriages are conjointly displaceable in the same direction while the first carriage and the support surface undergo relative motion in opposite directions with respect to each other. Copying material on which the image of the original is to be reproduced is transferred at a velocity substantially equal to the relative velocity of movement of the supporting surface and the first carriage, the second carriage being moved at a velocity substantially equal to one-half of the velocity of the first carriage.