The flatness of a precision surface plate is generally measured by using precision angular measuring instruments such as laser interferometers, autocollimators and electronic levels. Since these instruments are expensive and measurement procedures are complex, such methods are not widely used in industries. In this study, an electronic micrometer that is easy to use and inexpensive to produce was developed in order to solve this problem. The flatness of a black granite surface plate, measured using this device was compared with the values obtained by using the conventional three methods. The results were consistent within <TEX>${pm}1{mu}m$</TEM>. It proves that the flatness measuring method using electronic micrometers can be utilized for quantitative measurement. An accessory device that can improve the precision of measurement by attaching to the electronic micrometer was also designed and fabricated.