The arrestee was identified as Alam Khandaker alias Bishu Miah, 45, son of late Innos Khandaker of the area.
Acting on a tip-off, a team of police conducted a drive in the area and arrested Alam in the morning, said Sub-inspector Kabirul Haque of Bangabandhu Bridge East Police Station, also the investigation officer (IO) of the case.
Later, the accused gave confessional statement after being produced before the court of senior judicial magistrate Shamsul Alam.
The bus driver went into hiding just after the incident, said the IO.
Earlier, the bus supervisor Md Ershad and helper Nazmul Hossain were held and were sent to jail.
On August 30, the mentally disabled woman was raped by its driver and two of his accomplices in the bus on Bangabandhu Bridge-Dhaka highway near Ibrahimabad Rail Station at Bhuapur area of Tangail.