A method of producing a liquid crystal display device comprising the steps of opposing two substrates, which are composed of a transparent electrode formed on a plastic substrate, with a specified space therebetween, sealing the circumferential ends of the substrates with a sealant so as to form a sealed space, and injecting a liquid crystal to the sealed space, wherein a degassing treatment is conducted by heating each of the plastic substrates in a vacuum atmosphere to release gas adsorbed on the surface of the plastic substrate prior to either the step of forming the electrodes or the sealing step.