3 March 2017 Last updated at 14:42 GMT
The attack in Melton Mowbray on Wednesday afternoon was caught on CCTV.
Police said the man fled with "a quantity" of cash from the shop to a car parked nearby.
The woman, who worked at the shop, was treated in hospital for a cut to her head.
Officers said the attack could be linked to a similar attempted robbery shortly before.
A man with an axe has attacked and injured a woman in a robbery at a convenience store.