In accordance with one embodiment, a power supply apparatus includes a movable terminal section configured to be attached on or detached from and electrically connected with a fixed terminal section corresponding to the attaching or detaching of a unit on or from a main body; a sliding section configured to support the movable terminal section and slide; a guide stud which has a positioning section inserted into the guide hole of the sliding section, a shaft section smaller in sectional area than the positioning section and a connection section for connecting the positioning section with the shaft section, configured to guide the sliding section; and an elastic section configured to press the sliding section towards a unit terminal section.