The liquid treatment apparatus according to the present invention includes a substrate holder configured to horizontally hold a substrate, and a top plate configured to be rotatable and to cover the substrate held by the substrate holder from above so as to define a treatment space. In the treatment space, a chemical liquid is supplied by a chemical liquid nozzle onto the substrate, and an atmosphere replacement gas is supplied by a replacement nozzle into the treatment space. The replacement nozzle is supported by a replacement nozzle support arm configured to be horizontally moved between an advanced position at which the replacement nozzle support arm is advanced into the treatment space and a retracted position at which the replacement nozzle support arm is retracted outside from the treatment space. The replacement nozzle is configured to discharge, above the substrate, the atmosphere replacement gas upward.