Police found the builder, Veli Gocer, in Istanbul at a relative's house where he had gone into hiding after the 17 August quake, the private NTV television station said.
Mr Gocer is quoted as acknowledging that nearly 500 of the 3,000 units that he built in the town of Yalova came down in the quake, which measured 7.4 on the Richter scale. Mr Gocer also reportedly admitted to improper practices - such as mixing sea sand with concrete, producing buildings that crumbled when the quake hit - saying he didn't know any better. "No one ever told me I couldn't build with sea sand!" the Anatolia news agency quoted him as saying.
Police detained him in simultaneous raids on two Istanbul homes where they thought he might be staying. He was taken away, handcuffed, in an armoured vehicle. Police reinforced security around the building where he was being questioned in case of attack by earthquake victims. Mobs set fire to Mr Gocer's car in the first days after the quake, when he apparently had already gone into hiding.
Police have detained other contractors, some of them on charges of negligence. Several are believed to have fled Turkey.
The government crisis centre said the quake brought down 20,957 buildings, badly damaged 25,092 buildings and slightly damaged 27,609 others. The official death toll reached 15,135 yesterday.
Thousands of the quake victims in Yalova were entombed in their homes when cheaply built apartment blocks fell on top of them.
Turkey's contractors have been the object of public condemnation since the quake, accused of making a natural disaster a man-made one by building weak buildings of concrete mixed with sand, reinforced with thin iron bars.
International quake experts assembled at a conference in Potsdam, Germany, last week to assess Turkey's quake said the death toll could have been kept to a few hundred if building codes had been enforced and people had been educated about potential dangers.
Municipal authorities have been accused of taking bribes from contractors in return for approving their buildings.
Hundreds of survivors have petitioned the prosecutor's offices to determine blame for deaths and damages, as a prelude to lawsuits. Under Turkish law, contractors could be imprisoned for up to 10 years if found guilty of causing death through neglect. In most cases, however, defendants have been able to get away with paying fines if they have had no previous police record.
The government plans to set up temporary settlements of prefabricated homes to shelter more than 500,000 made homeless for the winter. (AP)