(1) Polyester fiber which consists substantially of polyethylene terephthalate, the fiber being characterized by strength of least 7.0 g/d, initial Young's modulus of at least 85 g/d, elongation of less that 20%, degree of crystallization X.rho. of at least 45% and the ratio of birefringence (.DELTA.n) and the degree of crystallization X.rho. from 0.38 to 0.45.(2) Method of making polyester fiber, characterized as follows: Polyethylene terephthalate is melt spun then passed through the heated cylinder which is installed directly under the spinning die; cooled and solidified; the oil agent is imparted and the yarn is taken-up at the speed of over 2000 m/min; this is drawn to a ratio of 1.5-2.3 in at least 2-drawing stages in continuation; then heat treated; the surface temperature of the drawing rollers at the final drawing stage is kept at 220.degree.-250.degree. C.; a non-contact type heating plate heated to a surface temperature of 250.degree.-500.degree. C. is installed 200-100 mm apart from the yarn at the final drawing stage to heat the drawn yarn; the yarn is heat treated again by the heating roller and finally wound-up.