@Akifumi Kimura - Guests can only view or comment on boards in a Team Plan, and you would have to add them add them to the specific boards that you want them to be able to view or comment on - more on the Guests feature here:

https://help.miro.com/hc/en-us/articles/360021415119-Collaboration-with-guests-BETA-

The only way someone can create boards in a Team Plan is to have a paid license/seat.

And the only way to have a non-team member edit boards that belong to your Team Plan is to use the Visitors feature:

https://help.miro.com/hc/en-us/articles/360012524559-Collaboration-with-visitors

@Robert Johnson 
Thank you for your comment.

Sorry for the lack of explanation.

Currently, I have purchased a paid license and have a team plan. I wanted to participate as a guest, but I was mistakenly registered as a member (full license). I want to change that person to a guest, but I don't know how.

There is no guest feature for the Team Plan.

You will have to use the Visitors feature if you want non-team members to edit for free. Have a read through this article:

https://help.miro.com/hc/en-us/articles/360012524559-Collaboration-with-visitors

@Robert Johnson 
It was solved by implementing it according to the article.

Thank you very much.