Hi @Madhu Sudan Singh ,
The wrong ServerRelativeUrl may cause the error.
It's unnecessary to add "/_api/web/GetFolderByServerRelativeUrl" in ServerRelativeUrl.
Take the following code as sample:
{
"__metadata": {
"type": "SP.Folder"
},
"ServerRelativeUrl": "https://<spname>.sharepoint.com/sites/SalesforceFiles/Shared Documents/<NewFolderNameToBeCreated>"
}
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.