Yamamura is a police officer and later an inspector from the Gunma district.

He only joined the police, because he was a fan of a TV show starring Shinichi's mother as a police woman. Yamamura makes a lot of mistakes and would never be able to solve a case if it wasn't for Conan. He is scared at the sight of blood and dead bodies and of ghosts. For these reasons no one takes him seriously and a lot of people make fun of him.

(Source: DCW Wikia)