Why tableview cell separator leave some space before?

Ans : 

Alternatively, you can also edit this in interface builder (IB):

1. Go to IB.
2. Select Table View.
3. Open "Attribute Inspector" on the right.
4. Change "Separator Insets" from Default to Custom.
5. Change the "Left" attribute from 15 to 0.

15 is default. So Left side space is seen before cell seperator.