“Kulsoom was stabbed eight times by her husband on Friday afternoon because she was working,” provincial police spokesman Noor Khan Nekzad told AFP.
“We have arrested the murderer, Abdul Rahim, who killed his wife,” Mr Nekzad said.
The couple had been married for six years and had two children.
The killing occurred nearly a week after a 20-year-old woman, Mah Gul, was beheaded in the same province by her in-laws after she refused to go into prostitution.
Abdul Qader Rahimi, the regional director of the government-backed human rights commission in western Afghanistan, said violence against women had dramatically increased in the region recently.
“There is no doubt violence against women has increased. So far this year we have registered 100 cases of violence against women in the western regions,” he said, adding that many cases go unreported.
Last year, in a case that made international headlines, police rescued a teenage girl who was beaten and locked up in a toilet for five months after she defied her in-laws who tried to force her into prostitution.