A holding base for removably holding an electronic device has a holding base body, a signal terminal provided in the holding base body, and connected to the electronic device in a holding position in which the electronic device is held, and a first connector attached to a surface of a printed circuit board, connected to the signal terminal, and connected to another electronic device. The printed circuit board is held by a bottom of the holding base body with the first connector held underneath the printed circuit board, such that a connecting port of the first connector faces a back side of the holding base body, and with an end edge of a front side of the holding base body positioned lower than an end edge of the back side thereof by an offset amount. The offset amount is set to be less than a thickness of the first connector.