Provided is a treatment method of being able to improve the obstruction of a biological lumen caused by stenosis of the biological lumen and the stagnation of a secretion. The treatment method includes a disposition step of disposing a dilation portion that can be dilated and deflated, and a collection portion, which is capable of removing a secretion S secreted from a biological lumen from a living body, in a stenosed site occurring in the biological lumen； a dilation step of widening the stenosed site after the disposition step by dilating the dilation portion in the stenosed site after the disposition step； and a removal step of removing the secretion from the living body by a removal portion.
