The behavior of viscous fingering in a Hele-Shaw cell under various gravity-levels was investigated using the drop shaft of the Japan Microgravity Center (JAMIC) and our high-gravity generator. When silicons oil was displaced by aqueous solution of potassium citrate through a rectangle Hele-Shaw cell which was made of two plane-parallel acrylic plates, a wave of the unstable horizontal interface between the two fluids was observed to take the form of viscous fingers. The wave number of viscous fingers decreased as the gravity level grew higher. It is confirmed that the experimental results of the wave number agreem with the prediction by a linear stability analysis, and that gravity tends to reduce the growth rate of the finger pattern if the density of the fluid with lower viscosity is greater than that of the fluid with higher viscosity.