Embodiments of the present invention provide a media drive that is intended for reduction in power consumption required for serial communications to/from a host, and a power saving method thereof. In one embodiment, a HDD includes: a cache; a host interface for transferring, to a host, transfer data read out from the cache; a host interface manager that controls the execution of commands so as to generate a transfer unnecessary period during which a command and transfer data need not be exchanged with the host; and a MPU that brings a serial communication part of the host interface into a power save mode during the transfer unnecessary period. The host interface manager determines the optimum data transfer timing of transferring data from the cache to the host on the basis of a transfer rate at which data is transferred to the host, and a read rate at which data is read out from a disk into the cache.