Solution treatment apparatus and cleaning method for solution treatment apparatus

A solution treatment apparatus for applying a coating solution onto a substrate, the solution treatment apparatus comprising:

• a substrate holding unit configured to hold and rotate the substrate;
• a coating solution supply nozzle configured to apply the coating solution to the substrate held by the substrate holding unit;
• a cup unit arranged outside the substrate holding unit in a manner to be able to surround the substrate held by the substrate holding unit;
• an exhaust path provided between the substrate holding unit and an inner peripheral surface of the cup unit;
• a coating solution collection unit provided above the exhaust path in a manner to cover the exhaust path and comprising an opening part communicating in a vertical direction;
• a solvent supply nozzle configured to supply a solvent for the coating solution to the coating solution collection unit;
• and
• a relay unit located above the coating solution collection unit and projecting from the inner peripheral surface, which is an inclined surface becoming lower toward an outer side in a radial direction, of the cup unit toward the coating solution collection unit in a gravity direction, wherein
• the relay unit projects directly and linearly, in the gravity direction, from a vertically middle part of the inclined surface of the inner peripheral surface.