mirror modifer behaves odd

Hi, I added the mirror modifier and turned the X axis and clippin on. It turned out the mirror of vertices misplaced like that. Why is that? How can I fix it?
Thanks…


your origin point is not central to the model. center it in object mode, then the mirror will work as expected

Also,

ctrl + A and apply rotation.

Many thanks! I should have thought of origin pivot set before…