Abstract: A measuring device includes a square ruler body provided with a plurality of scales, a plurality of marking lines, and a plurality of counting numbers. Each of the counting numbers has a corresponding numeral which is located under the respective the counting number for measurement of different directions. Thus, the measuring device is used to measure the size of the workpiece at any direction and any start point, thereby greatly saving the measuring time and the manual work. In addition, the counting numbers have a two-dimensional corresponding manner so that the measuring device can obtain the size of the workpiece instantaneously from left to right or from right to left without having to rotate or change the direction of the ruler body.