Disclosed is a method for fabricating a polyethersulfone nanofiber membrane with improved mechanical strength for water treatment by electrospinning. According to exemplary embodiments, the polyethersulfone nanofiber membrane possesses higher mechanical strength than conventional polyethersulfone nanofiber membranes that are susceptible to damage and limited in life when applied to water treatment processes. In addition, the polyethersulfone nanofiber membrane has high water permeability and can remove contaminants with high efficiency compared to conventional membranes for water treatment. Therefore, the polyethersulfone nanofiber membrane is suitable for use in water treatment.