An experimental. study is carried out to investigate the near-wake characteristics of an airfoil oscillating in pitch. An NACA 4412 airfoil is sinusoidally pitched about the quarter chord point between the angle of attack -6$^{circ}$ and +6$^{circ}$. A hot-wire anemometer is used to measure the phase-averaged mean velocities in the near-wake region of an oscillating airfoil. The freestream velocities of present work are 3.4, 12.4, 26.2 m/s, and the corresponding Reynolds numbers are 5.3${ imes}10^4$, 1.9${ imes}10^5$, 4.l${ imes}10^5$, and the reduced frequency is 0.1. Streamwise velocity profiles are presented to show the Reynolds number effects on the near-wake region behind an airfoil oscillating in pitch. All the cases in these measurements show that the velocity defects by the change of the Reynolds number are very large at the lowest Reynolds number $R_N$=5.3${ imes}10^4$: and are small at the other Reynolds numbers ($R_N$=1.9${ imes}10^5$ and 4.l${ imes}10^5$) in the near-wake region. A significant difference of phase-averaged mean velocity between 5.3${ imes}10^4$, and 1.9${ imes}10^5$ is observed. The present study shows that a critical value of Reynolds number in the near-wake of an oscillating airfoil exists in the range between 5.3${ imes}10^4$, and 1.9${ imes}10^5$.