There is provided an apparatus for continuously preparing an improved light receiving element for photoelectromotive force member or image-reading photosensor comprising the plural number of continuously connected reaction chambers through opening and shutting gates for forming respective constituent layers for said light receiving element and a substrate conveying belt moving through the reaction chambers, each of the reaction chambers having a film forming space, a gas supplying means being extended into the film forming space through the upper wall of the reaction chamber, an exhausting means being disposed at the bottom portion of the reaction chamber and the substrate conveying and supporting means being positioned in the reaction chamber, the said gas supplying means having (a) a conduit for transporting (i) a gaseous substance capable of contributing to form a deposited film and (b) a conduit for transporting (ii) a gaseous oxidizing agent being so disposed that the gaseous substance (i) and the oxidizing agent (ii) may be introduced into the space positioned above the surface of the substrate and they may be contacted each other in the absence of a plasma to thereby to generate plural kinds of precursors containing excited precursors and let at least one kind of those precursors directed to form a deposited film on the substrate on the substrate conveying belt.