An AC plug of a battery charger is arranged so as to be enclosed into a casing of the battery charger or projected therefrom when it is laterally rotated. The AC plug has two conductive blades and an edge surface for projecting them at an almost right angle. A first surface and a first rotary shaft are provided for a first side surface. A second surface and a second rotary shaft are provided for a second side surface opposite to the first side surface. A first contact portion electrically connected to one conductive blade is projected from the first rotary shaft. A second contact portion electrically connected to the other conductive blade is projected from the second rotary shaft. Conductive spring terminals which are elastically come into contact with the front edges of the first and second contact portions are provided for a board in the casing. By reducing a rotational radius of each contact portion, a small battery charger is provided.