Mesh problem after subdivision and boolean in blender I apply subdivision modifier both cylinder and mesh (watch), I boolean the cylinder on my mesh (watch) after that remove unwanted vertexes then bevel it, everything is fine except the four sides of hole kind of stretched, it's hard to see in solid mood but still there I'm using blender 2.9.
I really appreciate if someone help me.

Also ruined the shade.

In solid mode, it's hard to see the area where been stretched.
Your topology is probably not good, here is how you could do your object:

Create a 32 vertex cylinder and a 16 vertex cylinder:



Boolean:



Rework the topology:



Give it a Subdivision Surface modifier, add edge loops to sharp the edges:



Only apply the Subdivision Surface modifier if necessary, don't if you don't need to.