An electrical connection device is to be attached to a wiring board for holding a plate conductive member so that the wiring board is electrically connected to the plate conductive member. The electrical connection device includes a contact piece including an arm portion, a leg portion, and a base portion disposed between the arm portion and the leg portion; and a base member to be attached to the wiring board for supporting the contact piece at the base portion thereof. The base member is to be attached to the wiring board so that the base member is movable in parallel to the wiring board. The contact piece is arranged so that the plate conductive member pushes the arm portion to urge the leg portion against the wiring board with the base portion as a pivot when the plate conductive member contacts with the arm portion.