With Guptill's 16th ODI ton New Zealand won the second ODI match by eight wickets and led the series 2-0 against Bangladesh.
The home side took the unassailable 2-0 lead in the series scoring 229 runs by two wickets in 36.1 overs.
Earlier, Bangladesh were bowled out for 226 runs in the 50th over in the second ODI in Bangladesh tour of New Zealand, 2019 at Hagley Oval, Christchurch.
Mithun top scored with 57 runs off 69 smashing 7 fours and 1 six while Sabbir Rahman gets 43 off 65.
Ferguson picked three wickets up while two each for Astle and Neesham for the home side.
Kane Williamson, New Zealand captain, after the match said: “A clinical performance from us. We got a bit of overcast conditions, and a responsive surface in our favour. Martin Guptill was brilliant in the first game and just carried on in this game. Back to back hundreds - that's freakish.”
Bangladesh captain Mashrafe Mortaza, however, said: “It was a tough day. Mithun has kept scoring runs, that's a positive, but I think we have to score more heavily at the top. We need bigger partnerships like 60-70 runs rather than 30-40, so hopefully we can step up and give our best.”
Earlier, New Zealand beat visitors by eight wickets in the 1st ODI at McLean Park, Napier. Bangladesh were bowled out for 232 in 49th over with Mithun's 62 off 90.
The final ODI will be played on 20 February in Dunedin.