We developed a micro multipoint laser Doppler velocimeter (μ-MLDV) for noninvasive in-vivo measurements of blood flow and we presented the results of demonstrations performed on experimental animals. In this paper, we investigate the validity of power spectrum analysis for determining the flow velocity and the minimum power of the semiconductor laser in the μ-MLDV. Average velocity of blood flow was estimated from a peak position in the power spectrum. The laser power was reduced from 140 to 30 mW since 30 mW was the minimum power at which images of blood flow velocity in microvessels could be obtained. About 30 mW (power density of 15 mW/mm^2) is the maximum power which can be irradiated to humans. Further reduction in the laser power is necessary before this technique can be applied to humans.