To provide a barrier rib forming method that can form a low cost barrier rib by increasing utilization efficiency of the material, while improving quality and processing precision by simplifying the forming process and that also can form the barrier rib having a high aspect ratio.

The barrier rib is formed by moving the back plate S while injecting the partition wall material MW from a nozzle 17, and by promoting curing by illuminating light on the barrier rib material MW immediately after the injection from the nozzle 17 on the back plate S. When the light irradiates the barrier rib material MW immediately after the injection and its curing is promoted, the barrier rib material MW, which is injected on the back plate S in a line shape, maintains its shape, hence the forming process is simplified and a high quality and high precision barrier rib W can be formed. A low cost can be realized as the utilization efficiency of the material is increased.