A PET nonwoven fabric for a separator for a secondary battery includes first fibers composed of PET having a melting temperature of 240° C. or more and second fibers composed of PET having a melting temperature of 180˜220° C., respective fibers having two types of fibers having different diameters, and has a fine pore size and uniform pore distribution and exhibits superior surface properties, low surface defects, high mechanical strength and excellent mass production. Even when the temperature of a battery is increased to 200° C. or more, the PET nonwoven fabric has heat resistance which prevents thermal runaway and does not generate melting and shrinking.