The raid happened between 4.30pm and 4.45pm on Friday (July 8) at the Premier Store in Pytchley Court, Corby.
But a police spokesman said the man was confronted by the shopkeeper and was forced to escape on a pedal cycle with a second offender who was acting as a lookout.
He is described as being 5ft 11in with a medium build and he wore a grey jacket and a black woollen hat.
Officers want to speak to anyone who witnessed the incident.
Anyone with information can contact police on 101 or Crimestoppers anonymously on 0800 555111.