PURPOSE: To produce a rod lens which is defect-free and has smooth refractive indices by using a silicon compd. and a metallic compd. for dopant having a b.p. higher than that of said compd. as raw materials in a glass pipe and causing the same to react with each other by a plasma CVD method.

CONSTITUTION: The rate of supplying of gaseous raw materials from a raw material supply system 2 and the rate of evacuation of a vacuum suction system 3 are controlled so that the pressure in a quartz glass pipe 1 attains about 10Torr. The gaseous raw materials consist of a silicon compd. such as SiCl4, a metallic compd. for dopant having a b.p. higher than that of said silicon compd., such as AlC or TiCl3, and O2, etc. and are contained with an inert gas according to need. While plasma 6 is generated with a plasma generator 5, said gaseous raw materials are scanned in the longitudinal direction of the pipe 1 and are heated in a heating furnace 4 to cause thermal decomposition and vitrification, whereby an SiO2-Al2O3 or SiO2-TiO2 glass layer 7 of a prescribed refractive index distribution is formed. Such glass pipe 1 is collapsed and is further worked, whereby the desired rod lens is obtained.