I was not able to find it though I searched in Adobe updater website.
I know it can be downloaded from Solution Partner site. So now I'm looking for the public download link.
Where can I get the InDesign Server updater?
Have a look at the partner portal at "Software & Support" > InDesign SDK Software Downloads and find "Server" in the newly opened window, listing all CS2, CS3, and CS4 releasese and updates.