Foreign substance detection device and foreign substance detection method

A chemical liquid supply apparatus configured to perform a processing by supplying a chemical liquid to a substrate, the apparatus comprising:

• a flow path formation unit configured to form a plurality of flow paths through which the chemical liquid supplied to the substrate is flown and through which a light passes;
• a chemical liquid supply unit configured to supply the chemical liquid to the flow path formation unit such that the chemical liquid is supplied to a selected one of the plurality of flow paths;
• a laser light irradiation unit, commonly shared by the plurality of flow paths, configured to irradiate a laser light into each of the plurality of flow paths;
• a light receiving element, commonly shared by the plurality of flow paths, disposed to face the laser light irradiation unit with the flow path formation unit therebetween;
• a foreign substance detection unit configured to detect foreign substances in the chemical liquid based on a signal output from the light receiving element;
• and
• a moving mechanism configured to move the laser light irradiation unit and the light receiving element to a position corresponding to the selected one of the plurality of flow paths to detect the foreign substances in the chemical liquid supplied to the selected one of the plurality of flow paths.