Hi @최근창 · Welcome to QnA platform and thank you for your query.
Since you have already deleted on-premise ad in Azure IaaS, you need to first turn off directory synchronization so that you can delete the accounts in Azure AD.
To first turn off directory synchronization:
- Install MSOnline module by running
Install-Module MSOnline
PowerShell Cmdlet on Windows 10. If you're not running Windows 10, install the 64-bit version of the Microsoft Online Services Sign-in Assistant: Microsoft Online Services Sign-in Assistant for IT Professionals RTW. - Run
Connect-MsolService
cmdlet and sign-in using Global Administrator account of your Azure tenant. - Run
Set-MsolDirSyncEnabled -EnableDirSync $false
cmdlet to disable directory synchronization.
Once the directory synchronization is disabled, you will be able to delete synced users from Azure AD.
Note: Depending on the number of users in the directory, it may take few minutes to several hours (72 hrs max). Which is why it is not recommended to disable and enable directory sync very frequently.
Read more: Turn off directory synchronization for Microsoft 365
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