To highly accurately detect the residual capacity of a battery while an electronic apparatus is operating.

A reference load is selected (step SA2), and a battery switching order (connection order) is created (step SA3). In the switching order (1), the residual capacity of a battery connected to the reference load selected in the step SA2 is detected (step SA4). The operation state of the reference load in detecting the battery residual capacity is stored (step SA5). The reference load is switched based on the battery switching order created in the step SA3 (step SA6). When the reference load becomes the operation state same as the operation state stored in step SA5, and at this time point, the residual capacity of the battery connected to the reference voltage is detected (step SA7). It is determined whether the detection of the residual capacities of all the batteries are completed or not (step SA8), and the processing from the step SA6 is repeated until the completion.