Substrate processing apparatus and substrate processing method

A substrate-processing apparatus, comprising:

• a reaction tube which has an opening at a bottom thereof and in which substrate processing is performed;
• a boat which is introduced into and taken out from the reaction tube through a boat-lifting unit and on which multiple substrates are seated in a vertical direction;
• a substrate-loading part which is placed under the reaction tube and in which a loading area is formed, the multiple substrates being loaded and unloaded into the boat in the loading area through a substrate transfer robot;
• an external air inlet which is formed on one side of the substrate-loading part, is connected to the loading area such that external air is introduced into the loading area, and controls an amount of the introduced external air;
• a gas control device which controls an injection amount of inert gas supplied into the loading area;
• a particle-measuring sensor which measures particle information of the loading area;
• and
• a controller which controls one or more of the external air inlet and the gas control device according to the particle information received from the particle-measuring sensor to reduce particles in the loading area.