The woman was outside near the train station when she was suddenly attacked by an unknown assailant armed with a large kitchen knife.
The man stabbed her several times, including three times in the back, before she collapsed. She then fell down on the train tracks.
The woman was taken to the central hospital in nearby Västerås with serious, but not life threatening wounds.
“The only thing she said was that she’d never seen this man before,” said Västmanland police spokesperson Per Strömbäck to the TT news agency.
Police subsequently launched a large-scale operation to find the woman’s attacker.
Later Thursday evening police reported the arrest of a 22-year-old man at the suspects home in Hallstahammar on suspicions of attempted murder.
Police also found the knife in some bushes about 20 metres from where the woman was attacked.
During questioning by police, the 22-year-old admitted to stabbing the woman.
“The confession came during an interrogation. He can’t provide any motive for the attack. She was in the wrong place at the wrong time,” said Strömbäck.