A light source device includes a detector that detects a remaining capacity, and a prediction calculation circuit that calculates a capacity consumption predictive value indicating a ratio of consuming a capacity of a supply source within a predetermined period of time in each illumination mode. The light source device further includes a capability calculation circuit that calculates a driving capability of the supply source corresponding to each of the illumination modes, based on the remaining capacity and the capacity consumption predictive value; and a reporting unit that reports the driving capability.