To provide a hot water temperature stabilizing device capable of safely supplying a hot water sent from a hot water supply unit at a relatively stable temperature with a simple structure and a mobile bathing vehicle using the same.

The hot water temperature stabilizing device comprises an input water tube 10 for introducing the hot water sent from the hot water supply unit, an output water tube 11 for externally discharging the hot water, and an agitating tank 12 formed in parallel with a cross section of the tube 10 or the tube 11 to agitate the hot water introduced from the tube 10 between the tube 10 and the tube 11 and having a larger area of its section than the cross sectional area of any of the tube 10 and the tube 11.