The passengers included teenage athletes who reportedly screamed and cried in panic. Video showed air blasting through the cabin, whipping some passengers' hair. Other passengers suffered severe ear pain and breathing problems after the door opened.
Footage shows the terrifying moment inside a cabin after a passenger opened an emergency exit door on a South Korean plane shortly before it landed.
Some people on board the Asiana Airlines flight tried to stop the person from opening the door but it was eventually opened partially, the transport ministry said.
The plane, with 194 people on board, was heading to the southeastern city of Daegu from the southern island of Jeju.
The flight normally takes around an hour and the incident occurred when the plane was approaching the Daegu airport at an altitude of 700ft (213m).
It was not disclosed how long the door was open.
The passengers included teenage athletes on their way to a track and field competition and some screamed and cried in panic, Yonhap news agency reported, citing their coach.
It quoted other passengers saying they suffered severe ear pain after the door opened.
Some cabin crew shouted for help from passengers to prevent the door from being opened, the news agency said.
The transport ministry later said the person who opened the door had been detained.
Pictures showed officers in plain clothes arresting a passenger.
The ministry said police had taken the passenger into custody and were investigating a possible violation of aviation safety laws.
Their motive was not known.