To provide an information processor, a power mode control method, a power mode recording program, and a recording medium for achieving power saving by excluding any unnecessary packet processing in a normal power mode, and smoothly shifting the normal power mode to a power saving mode.

This information processor is configured to shift a normal power mode to a power saving mode when any packet is not processed by a first control means in at least a fixed period, and provided with a packet table in which a packet to be processed by the first control means is registered and a judgment means for judging whether the normal power mode can shift to the power saving mode in this system. When judged that the normal power mode of this system can shift to the power saving mode in the normal power mode by the judgment means, a network controller part processes the packet on the basis of the packet table.