Bandit took away cash from a grocery store at Laajalampi area in Mikkeli on Saturday afternoon, police said in a press release.
The alleged masked robber stormed into a Sale grocery chain shop at about 2:00 pm and threated the shopkeeper with a hammer.
At certain stage the bandit snatched a small amount money from there and left the scene as there was no customer or other staff at the shop during the incident.
Responding to an alarm, police rushed to the spot and conducted extensive search at the locality.
They later arrested the 20 years old suspect based on the description given by the shopkeeper and recovered the looted money from his possession.
Police, however, did not divulge the detail identity of the alleged bandit.
The police are investigating into the case as aggravated robbery.