The incident happened at about 9:30am on Thursday, December 29, when a man entered business premises in High Street, Westtown, in Dewsbury, and made demands for cash.
The shop assistant refused and the suspect, who is believed to have been carrying a knife, fled empty handed.
Police are keen to trace a man who was said to be wearing dark clothing. He is believed to have fled onto St John’s Parade.
PC Luke Mitchell, of Huddersfield CID, said: “This was undoubtedly a terrifying attack on a lone member of staff who has worked in the community for many years.
“CCTV enquiries have shown that there were a number of members of the public in the area at the time and I am appealing for them to come forward to assist police with our enquiries.”
Anyone with any information is asked to call PC Luke Mitchell in Huddersfield CID via 101, quoting crime reference 13160757147, or the independent charity Crimestoppers on 0800 555111.