One of the objects of the present invention is to provide an system which can detects degradation in a driving mental state of a driver, that is, sleepiness, fatigue, fret, and so on during driving of a vehicle and notifies the driver of the degradation to encourage safe driving and can reproduce sound such as music matching the taste of the user such as a driver while maintaining awakening of the driver of a mobile unit.The reproduction controlling system for a mobile unit, is provided with a system controlling reproducing device for reproducing a piece of sound data stored in a database during traveling of the mobile unit, a driving information acquiring device for acquiring driving information indicating a driving state of the mobile unit, the driving information including at least heartbeat variation information, an audio component information acquiring device for analyzing an audio component included in the sound data and acquiring audio component information, a judging device for judging mental and physical states of the driver based on the acquired driving information, a selecting device for selecting the sound data to be reproduced; and a control device for controlling the reproducing device to reproduce the selected sound data.