Provided is a treatment tool exchanging device that switches and holds a plurality of treatment tools for treating a target to be treated. The treatment tool exchanging device includes a flexible insertion part into which the plurality of treatment tools are inserted and in which a plurality of treatment tool channels for defining insertion paths for the treatment tools are formed, a driving part that advances each of the plurality of treatment tools, a manipulating part that manipulates the plurality of treatment tools to perform treatment, and a control unit that controls the amount of protrusion, from the treatment tool channel of the treatment tool, which has protruded from a distal end of the treatment tool channel, among the plurality of treatment tools. The insertion part has a switching part that changes the insertion path of the treatment tool to be inserted.
