The victim had just deposited the cash at around 6.10pm at the branch next to the Almondvale Centre in Livingston. The suspect grabbed him and demanded that he hand over property. When the victim refused, the would-be robber made off on a footpath towards the Dedridge area.
He is described as white, 6ft tall, 30 to 40 years old, broad shouldered, heavy set, and wearing a blue anorak with the hood up, and a scarf over his face. He had dark trousers, a dark top and short dark hair.
A Police Scotland spokesman said: “We are appealing to anyone who may have witnessed the incident to come forward.
“Likewise, we would like to hear from anyone who was in the area, who may have noticed the suspect either before or after the incident took place, or who recognises his description.”
Anyone with information is asked to contact police on 101, or alternatively make an anonymous report through the charity Crimestoppers on 0800 555 111.