Abstract: A process for producing a light guide body is disclosed. A polymer composition is prepared from a polymer and a solidifying agent. The solidifying agent has an operative temperature at which the solidifying agent is, operative to solidify the polymer, wherein the operative temperature is higher than or equal to the Tg of the polymer. The polymer composition is heated to melt at a temperature higher than Tg. The molten liquid of the polymer is molded and cooled so as to solidify at the operative temperature of the solidifying agent. Preferably, the molten liquid is cooled rapidly to a supercooled liquid state during the molding step. Due to the high expansion coefficient of the supercooled liquid of the polymer, there are changes in thickness and density in part of a molding from the molten liquid. The process produces a light guide body having concave or convex surfaces without using an expensive patterned mold.