Hardness is defined as a scale to evaluate the resistance of an object against the force of an impression. Throughout their long history, hardness tests have acquired more and more applications in line with growing attention to the mechanical properties of industrial materials. The more advanced the materials, the greater accuracy is required when testing their hardness, attracting attention to a broader range of parameters which includes the geometry of indenters, loading conditions, and methods for measuring impressions.The purposes of hardness tests have also expanded to include the evaluation of material strength and microstructural changes as a factor of hardness and to guarantee product quality.The level of quality control required for hardness testing machines is highly dependent on their applications. Given this complicated situations, this paper deals with some basics for effectively using the scale of hardness.