Firstly your question is not clear. I will assume it is a web developer, and yes developer can be a UI/UX designer reason a web developer just develops a product without any thought but UI/UX designer consent to the look and design along with user experience about the product. So the developer with the knowledge of UI/UX tools can ultimately build a successful product. If you are interested in learning this technology then I recommend you to take up this UI UX training course from Intellipaat which doesn’t require any previous knowledge course is designed in such a way that anyone can learn this from basic to advance levels easily.
For your reference, I am attaching a free UI/UX training video do check out this -