District superintendent of police Syed M H Mirza said relations had been sour between the couple, who were married in 2000 and have two sons nine and six years old, over the alleged affair.
The woman had left her family home at Ichapur and was staying with the other person for the past one and half years.
Her husband, who had traced her, waited outside her house with a knife during the day and finding her alone hacked her to death, he said.
When the neighbours rushed in the man gave himself up. He was later handed over to the police.