Q: My new iphone 5s is getting hot while using internet , so pls tell me this is usual or any problem with my phone?

Hi mukk25, 

Welcome to the Apple Support Communities!

I know it can be concerning when the temperature of the iPhone is warmer than you would expect. Please review the attached article for information on operating temperatures. 

Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures

When using the device or charging the battery, it is normal for it to get warm. The exterior of the device functions as a cooling surface that transfers heat from inside the device to the cooler air outside.

Have a great day, 

Joe