how to check magic mouse is original or not?

Unfortunately we do not know where you are located so cannot guide you to your nearest Apple store. Where did you buy this magic mouse and what exactly leads you to think it is not genuine. If you could take a photo (both the mouse and the underside) and post it here, that would help.

From what I can see that is the Magic mouse which Apple sell. It matches my own in almost every respect and the only difference is the serial number (of course). I hope this reassures you.