I can't scale the size of UV texture image I was making this tile following a tutorial.
I was usually able to scale UV texture simply in the UV editor screen.
However this time, although I did the scaling as I wanted the tiles to appear bigger and larger, it looks exactly the same, very dense. 
How can I fix it?
Thank you so much!
Looks like you have 2 UV sets. So to use one of them put UV map node in material, and select right one: 



Then, connect UV map node to textures: