Hello 易儒 李,
Thank you for posting your question in the Microsoft Q&A Community.
I understanding that you would like to know if its possible to change the VNet your VM is attached to.
Please note that you cannot change the Virtual Network where your machine is attached to directly but there is a work around mention in a related forum.
Follow the link to the forum to get more information about this.
https://learn.microsoft.com/en-us/answers/questions/959032/move-vms-to-another-vnet-in-same-region
Let me know if further assistance is needed.
Babafemi