Police say two men targeted the Hanging Heaton food store on Mill Lane just after 9pm on Friday night.
"It is believed both of them were armed," West Yorkshire Police said in a statement.
"They then demanded money before the shopkeeper was assaulted. A mobile phone was then stolen. The victim was left with cuts and bruises as a result of the incident."
Anyone with information is asked to call West Yorkshire Police on 101 quoting reference 13180019819.