To provide a storage tank device for vehicle washing water requiring no heavy labor for the fitting/removing work of a bucket, having a long life, and having no possibility of splashing another vehicle or the like with the sewage to be brought back.

In this storage tank device for vehicle washing water, a tank 4 storing the water washing a vehicle is held by the holding member 3 of the tank 4, and the holding member 3 can be reciprocated and rotated by the prescribed angle in the horizontal direction. The holding member 3 is fixed to part of a vehicle body, and the tank 4 is pivotally fitted to the holding member 3 rotatably in the vertical direction.