A connection device includes a rod-shaped electrode, a plurality of cylindrical electrodes through which the rod-shaped electrode passes, the plurality of cylindrical electrodes being sequentially exposed on a surface in order from a front end side of the rod-shaped electrode, an insulation section configured to insulate the rod-shaped electrode and the plurality of cylindrical electrodes from each other, and a plurality of connection terminals electrically connected to the rod-shaped electrode and the plurality of cylindrical electrodes in a vicinity of a rear end of the rod-shaped electrode, the plurality of connection terminals being protruded from a rear side.