I am developing an application where user has to write some information. For this purpose I need a UITextField which is multi-line (in general UITextField is a single line).
As I'm Googling I find a answer of using UITextView instead of UITextfield for this purpose.
UITextField is specifically one-line only.
Your Google search is correct, you need to use UITextView instead of UITextField for display and editing of multiline text.
In Interface Builder, add a UITextView where you want it and select the "editable" box. It will be multiline by default.