Is there any way to make simple chart graphics like Excel charts using Unity?
About everything is possible, but you have to build it yourself. There isn't really support for drawing vector graphics, so it will be quite a challenge.
Try UnityPaint from Aron Granberg's website. It is a library which can plot points and draw lines to a texture. Once you have drawn the graph to the texture, you can assign it as a GUIContent for a UnityGUI window.
You could fake it by creating a graph background image, then placing primitive game objects like cubes into the the graph. By scaling a cube, you could create a bar chart.