Substrate treatment apparatus and substrate treatment method

A substrate treatment apparatus for supplying a treatment liquid to a substrate and treating said substrate, the substrate treatment apparatus comprising:

• a substrate retaining part that retains said substrate;
• a discharge nozzle that discharges said treatment liquid to said substrate retained by said substrate retaining part;
• a storage tank that stores in said treatment liquid;
• a supply piping part that is connected to said storage tank and forms a supply passage through which said treatment liquid to be supplied to said discharge nozzle passes;
• a return piping part that is connected to said storage tank and forms a return passage through which said treatment liquid passed through said supply piping part is returned to said storage tank;
• and
• a gas supply part that supplies an additive gas different from a removal target gas dissolved in said treatment liquid into said return passage of said return piping part, wherein
• a distal end of a gas supply pipe of said gas supply part forms a jet opening that jets said additive gas in said return passage of said return piping part;
• said jet opening is configured to discharge said additive gas in a first direction, which is opposite to a second direction in which said treatment liquid flows;
• and
• all of said additive gas is discharged from said jet opening in said first direction,
• in said storage tank, a release opening of said return piping part is opened toward a third direction intersecting with a vertical direction, different from a fourth direction of said release opening to a suction opening of said supply piping part, such that said treatment liquid is released from said release opening such that it is directed away from said suction opening.