I have some water stains on my ceiling as the picture shows below. I couldn't figure out if this is a roof leaking or the condensation in attic. Please help.
To me, it doesn't look like it's coming from above. It looks like something splashed on the ceiling, or condensation formed on the ceiling.
If this is a bathroom or kitchen, try running the exhaust fan during showers and while cooking.
The only way to be sure it's not coming from above, is to get up in the attic and have a look around.
I see the light circular stains that you have described. It looks like water stains that have formed from water that has seeped through the drywall ceiling. I would use a water + dish soap + bleach solution and thoroughly clean the ceiling. If possible, I would put a small plastic barrier above the ceiling in the attic. If the moisture is from the attic area, then the barrier should redirect moisture away from the ceiling below the barrier. So later on, if you see the same spots in nearby areas--but, not on the ceiling area that is below your plastic barrier, then you can be pretty sure the moisture is coming from the attic & slowly weeping through your drywall ceiling.
If the ceiling that you have shown is in a bathroom that doesn't have good ventilation, I suggest you install a ventilation device or leave the door open to vent humidity out of the bathroom.
Maybe plumbing pipes or AC unit in the attic.