A method of manufacturing a liquid crystal display panel where a image display cell region and a plurality of dummy cell regions are provided on a glass substrate. The dummy cells are formed to monitor the internal pressure of liquid crystal sealed in the image display cell region. Liquid crystal is dropped on the image display cell region and the dummy cell regions and the glass substrate and a second substrate are bonded together. The image display cell and the dummy cells, which have the liquid crystal sealed therein, are formed in the image display cell region and the dummy cell regions, respectively. Based on the results of monitoring states of the dummy cells thus formed, a state of the image display cell is estimated.