To achieve performance and a function excellent in a host connection mode and a simplex operational mode.

An information processing unit 10 has a liquid crystal display 20, an MO drive 44 and a memory card slot 28. When connection with a host 12 is determined, a main processor 32 controls a sub-processor 34 for a USB bridge to be in an operational state so as to execute input/output processing with the host 12. When a processing request of an operation part 22 is determined, the main processor controls the sub-processor 34 for the USB bridge to be in a non-operational state and makes the unit operate separately. The main processor 32 pulls up a specific signal line D+ by which the sub-processor 34 for the USB bridge is connected to the host 12, thus controlling the sub-processor 34 for USB bridge to be in the operational state.