Provided is a method for washing a treatment tool stand that can efficiently perform the operation of washing the treatment tool stand in a short time without taking substantial time and effort. The method for washing a treatment tool stand related to the invention is a method for washing a treatment tool stand of an endoscope using a stand washing tool having a first washing member formed to a first height position and a second washing member formed to a second height position lower than the first height position. The washing method comprises a first washing member inserting step of inserting the first washing member into a gap between a stand storage wall section of the endoscope and the treatment tool stand； a second washing member abutting step of making the second washing member abut against a treatment tool guide surface of the treatment tool stand； and a stand washing tool moving step of moving the stand washing tool along the treatment tool guide surface in a state where the first washing member is inserted into the gap and the second washing member is made to abut against the treatment tool guide surface.
