A quantum device (100) includes: an interposer (112); a quantum chip (111); a first connection part (130) that is provided between the interposer (112) and the quantum chip (111) and electrically connects a wiring layer of the interposer (112) to a wiring layer of the quantum chip (111); and a second connection part (140) that is provided on a main surface of the interposer (112) where the first connection part (130) is arranged and is connected to a cooling plate (115).