A supporting base for an electronic device includes a mounting plate and two standing pieces. The two standing pieces are rotatably fixed to the mounting plate. The two standing pieces can rotate from a closed position to an open position. When the two standing pieces are in the closed position, the mounting plate supports the electronic device in a first manner. When the two pieces are in the open position, the two pieces clamp the electronic device in a second manner. An electronic device assembly is also provided.