Molecular orientation mechanism in fiber drawing process was discussed with the measurement results of birefringence and thermal shrinkage for unoriented amorphous poly (phenylene sulfide) (PPS) fiber. The drawing conditions were as follows; drawing temperature 90-110°C, drawing rate 0.005-0.040/s, draw ratio 1-4. Drawability of PPS fiber showed a sharp increase above 90°C, and also showed ‘super-draw’ phenomenon at 110°C. Strain induced crystallites which can be observed with X-ray diffraction were formed in the samples whose birefringence exceeded about 0.10, while the samples whose birefringence were within 0.06 to 0.10 contained oriented crystalline embryo because they indicated self-elongation and orientation increase in the thermal shrinkage process. The apparent relaxation times estimated with assuming upper-convected Maxwell model showed temperature dependence whose activation energy corresponded 50 to 80kJ/mol, and also showed obvious draw rate dependence and draw ratio dependence. Mechanical properties of drawn fibers at room temperature showed good relationships with the birefringences.