An experimental study was carried out in order to investigate the influence of Reynolds number on the near-wake of an oscillating airfoil. An NACA 0012 airfoil was sinusoidally pitched at the quarter chord point, and is oscillated over a range of instantaneous angles of attack of $pm$6$^{circ}$. An X-type hot-wire probe was employed to measure the near-wake of an oscillating airfoil, and the smoke-wire visualization technique was used to examine the flow properties of the boundary layer. The free-stream velocities were 1.98, 2.83 and 4.03 m/s and the corresponding chord Reynolds numbers were 2.3$ imes$104, 3.3$ imes$104 and 4.8$ imes$104, respectively. The frequency of airfoil oscillation was adjusted to fix a reduced frequency of K=0.1. The results show that the properties of the boundary layer and the near-wake can dramatically be distinguished in the range of Reynolds numbers between 2.3$ imes$104 and 3.3$ imes$104, on the other hand, it is similar in the cases of Re=3.3$ imes$104 and 4.8$ imes$104. This is caused by that the unsteady separation point is dramatically delayed in case of Re= 2.3$ imes$104.