Measurements of the vapor-liquid coexistence curve near the critical point were carried out for 1,1,1-trifluoroethane (R-143a) in the reduced temperature range of 0.97 < T/T-c < 1 and in the reduced density range of 0.45 < rho/rho(c) < 1.53. Taking into consideration of the disappearing level of the meniscus as well as the intensity of the critical opalescence, the critical temperature T-c and critical density rho(c) were determined. With respect to the critical pressure P-c, we calculated the value from the new vapor-pressure equation made by ourselves in order to represent the behavior of vapor-pressures near the critical point. The critical parameters determined in this paper are T-c = 345.88 + delta(T) K, delta(T) = 0.00 +/- 0.01 K, rho(c) = 431 +/- 3 kg m(-3), and P-c = 3764 + 78.73 delta(T) +/- 5 kPa. In addition, the critical exponent beta along the coexistence curve was also discussed.