Two men entered the One Stop store in High Street at about 9.45pm last night, with one then producing a small black handgun.
He demanded cash from the employee and the pair then left through the front door.
Police are appealing for witnesses and say both men were were wearing gloves.
No further descriptions are available at this stage of the investigation.
Investigating officer, DC Alex Beever of Force CID, said: “I would appeal to anyone who saw anything suspicious in the area at the time to contact the police immediately on 101 and quote reference 4395758/14.