By use of the chamber combustion flame method which utilizes an oxyacetylene flame torch contained within the chamber, we have discovered the possibility of fabricating relatively thick diamond films or high-quality diamond disc sheets that may be utilized for various optical or electronic applications. The sheets have the disadvantage, however, of poor uniformity of thickness that has yet to be solved. In this paper, we propose an improvement of the chamber combustion flame apparatus comprising a swinging torch structure that can contribute to a significant improvement in the thickness distribution without sacrificing the fundamental advantages of the chamber combustion flame method, i.e. high quality in terms of Raman characteristics, optical transparency and the cathodoluminescence characteristic, as compared with the conventional open air combustion flame method.