center of the top wall 12 so as to align the optical axis x p of the projection lens system 15 with the normal line y p of the transparent stage surface 12 and focus an image on a screen 5 standing vertically and located remote from the overhead projector ohp it is inevitable that the normal line y p of the transparent stage surface 12 is inclined the angle of u03b8 a relative to a vertical axis v the frame 16 is further integrally formed with a pair of brackets 19 for supporting a pivot rod hidden in fig2 by which a reflective mirror 18 is pivoted so as to turn about the pivot rod namely a horizontal line as was previously described and schematically and clearly shown in fig1 the top wall 12 of the box shaped stage 10 is tilted or inclined the angle of u03b8 a relative to the vertical axis v in which the light source 11 is located or otherwise relative to a horizontal surface h s on which the box shaped stage 10 is placed similarly the projection lens system 15 is tilted so as to direct its optical axis x p inclined the same angle of u03b8 a relative to the vertical line v or relative to the horizontal surface h s in.