How to set single permallink.

Hi, there.

My site has 2 permalink each category.

https://vitt.co.kr/vitt-collection/
https://vitt.co.kr/category/vitt-collection/

I want to have https://vitt.co.kr/vitt-collection/
instead of https://vitt.co.kr/category/vitt-collection/

My wordpress setting of Permalink is /%category%/%postname%/
I don’t think this is wrong.
Please let me know how to solve this problem.

Thanks in advance.
Jin