This paper presents a method for non-destructive inspecting micro-holes with diameters of less than 100μm by using audible sound. Fluid flow through micro-holes affects the performance of a product. Therefore, if the flow rate of fluid passing through micro-holes could be accurately assessed by means of an inspection system, it would be possible to guarantee the performance of the product. By using a low frequency sound in micro-hole inspection, it is possible to measure the hole diameter differences of 1μm when hole diameter is 100μm. In addition, the experimental results show that, by setting the appropriate frequency, it is possible to measure faster than conventional inspection method.