Can anybody tell me that how to check if someone created his site using wordpress?
Wappalyzer is a cross-platform utility that uncovers the technologies used on websites. It detects content management systems, ecommerce platforms, web frameworks, server software, analytics tools and many more.
The tool is available as a browser extension.
Though the results aren't always accurate, and since WordPress can be easily identified by scanning the HTML contents then 99% of a time it gets WordPress easily.