A playback device includes a playback function unit, a data signal monitoring unit configured to output a data change trigger signal based on a change in the data signal, a clock signal monitoring unit configured to output a clock change trigger signal based on a change in the clock signal, an enable signal monitoring unit configured to output an enabled/disabled state signal that indicates a disabled or enabled state of the enable signal, and a determining unit configured to determine whether the data signal, the clock signal, or the enable signal is properly inputted into the playback function unit or not, based on the data change trigger signal, the clock change trigger signal, and the enabled/disabled state signal.