Straight-through microchannel (MC) emulsification is a promising and novel technique for producing monodisperse emulsions. A straight-through MC is a channel array microfabricated vertically to the surface of a silicon plate. We investigated the throughput capacity of monodisperse oil-in-water (O/W) emulsion droplets for a silicon straight-through MC plate with a size of 40 x 40 x 0.4 mm, developed in this study. Oblong channels used in this study had a longer line of 26.7 mu m, a shorter line of 6.6 mu m, and a depth of 100 mu m. Monodisperse O/W emulsions with average droplet diameters of 31-32 mu m and coefficients of variation below 10% were successfully produced using the large straight-through MC plate. The straight-through MC emulsification device had maximum throughput capacities of monodisperse emulsion droplets of 20-30 mL/h for the system containing refined soybean oil and of 60-70 mL/h for the system containing silicone oil.