An object is to provide a highly reliable liquid crystal display device which includes a liquid crystal layer exhibiting a more stable blue phase. Another object is to provide a method for manufacturing a liquid crystal display device with high yield. Polymer stabilization treatment is performed as follows: a photocurable resin is added to a liquid crystal material exhibiting a blue phase, and the photocurable resin is selectively polymerized by scanning a liquid crystal layer provided between a first substrate and a second substrate with light in a certain direction. Thus, a first region where the light irradiation treatment is performed and a second region where the light irradiation treatment is not performed are formed in the liquid crystal layer. Since polymerization of the photocurable resin proceeds in the first region, the polymerization degree of the photocurable resin in the first region is higher than that in the second region.