Evaporation is the process by which a substance transitions from its liquid phase to its gas phase. This paper uses Parallel Four-Step Phase-Shifting Interferometry (PFSPSI) to quantitatively measure the mole fraction of acetone vapor surrounding a single ultrasonic-levitated acetone droplet with a diameter of several hundred microns. The results indicate a non-symmetric vapor concentration pattern, attributed to the uneven pressure distribution on the droplet’s surface. The vapor concentration is higher above the upper surface of the droplets than beneath the lower surface even though acetone vapor is heavier than the air. It is also observed that the round averaged mole fractions of different droplets increase with the droplets’ size, while the mole fractions at the upper vertex and side vertex increase faster than it at the lower vertex. These observations align with numerical simulations found in the literature and is considered as resulting from the acoustic streaming generated by the ultrasonic-levitator.