The quake struck at about 4 am on Saturday at the beginning of the Lunar New Year holiday, with almost all the dead found in Tainan's toppled Wei-Kuan Golden Dragon Building. Two people died elsewhere in the city.
Rescue work has focused on the wreckage of the 17-storey building, where more than 100 people are listed as missing and are suspected to be buried deep under the rubble.
No survivors have been brought out since Monday evening.
Questions have been raised about the building's construction quality, especially materials used to build it.
Hsiao Po-jen, director of the legal affairs department of the Tainan city government, told Reuters that Lin Ming-hui, the Wei-Kuan Golden Dragon Building's developer, had been arrested on suspicion of negligent homicide on Monday evening.
Hsiao said the information came from police and prosecutors.
Reuters witnesses at the scene of the collapse have seen large rectangular, commercial cans of cooking-oil packed inside wall cavities exposed by the damage, apparently having been used as building material.
Taiwan media has also reported the presence of polystyrene in supporting beams, mixed in with concrete.
The Wei-Kuan, completed in 1994, was the only major high-rise building in the city of 2mn people to have completely collapsed.
Its lower storeys, filled with arcades of shops, pancaked on top of each other before the entire U-shaped complex toppled in on itself.
Deputy Tainan Mayor Tseng Shu-cheng told family members that 103 people were still missing in the rubble.
