Should I need to learn drawing beside programming?

I personally don't believe that you need to be skillful at drawing or art, in general, to be able to make games, regardless of the engine you're making them in. A common thing for many indie programmers to do is to make "programmer art", sticking to simple shapes and colors, and using code and equations to generate interesting visuals. To be able to make something visually interesting out of that requires some effort, yes, but if you're not interested in learning art, that's the way to go.

If you ARE interested in learning how to draw, there are plenty of resources you can use. Everything from courses on human anatomy to tutorials on how art programs work. Many incredibly skilled and generous people have created free tutorial series for art.

Regardless of the path you take, I definitely recommend you at least learn color theory and maaaaybe composition. All in all, it's up to you. Best of luck! :)

@santunu23 the quick response is "No", provided someone else does it for you ;-). But it's not just Drawing, maybe you'll need 3D models too, and music, and sound FX, and visual FX, etc. It's almost impossible to be proficient in ALL of these skills. But you can get the assets you need for your project, either in the Asset Store (Free/Paid): https://assetstore.unity.com/ Or find others to do it for you, either by paying them or teaming up with them in Unity Connect: https://connect.unity.com/home