The victim was approached by the group and ran into Taggar Sweet Centre on High Street.
They followed him inside where he was punched, kicked and had his iPhone, cash, bank book, passport and bag stolen, officers said.
Sandwell Police posted on Facebook saying: "Do you have any idea who these four men are?
"We want to speak to them about a street robbery inside a shop on High Street, West Bromwich near to Shaftesbury Street on Friday, November 27.
"At around 3pm, a man was approached by a group of men, fearing he was about to be robbed he ran into the Taggar Sweet Centre. The group followed him and he was punched, kicked and had his iPhone, cash, bank book, passport and bag stolen.
"Enquiries continue and anyone with information is asked to contact us via Live Chat at west-midlands.police.uk between 8am and midnight, or call 101 anytime. Crimestoppers can be called anonymously on 0800 555 111. Please quote crime number 20SW/293687A/20."