In a case where a first AC adaptor with a small capacity is connected to a notebook personal computer, an electronic apparatus supplies electric power supplied from the first AC adaptor or electric power as a sum of the electric power supplied from the first AC adaptor and electric power supplied from a battery to the load (3), depending on a load state (power consumption). According to this configuration, irrespective of the amount of the power consumption at the load (3), it is possible to connect the first AC adaptor with a small capacity to the notebook personal computer so as to operate the load (3). The AC adaptor with a small capacity is downsized and reduced in weight since in general it has a smaller transformer (transforming circuit) in comparison with a large-capacity AC adaptor.