PURPOSE: To prevent air from flowing into a reaction chamber even if substrates are successively transferred into the reaction chamber in a continuous treatment.

CONSTITUTION: A chemical reaction apparatus is equipped with a first buffer chamber 1, a reaction chamber 2, a second buffer chamber 3, a rinsing chamber 4, and a drying chamber 5, which are successively arranged in this sequence. A first, gate valve 40 is provided to the substrate loading opening 51 of the first buffer chamber 1, a second gate valve 41 is provided to a communicating hole 52 which enables the first buffer chamber 1 to communicate with the reaction chamber 2, a third gate valve 42 is provided to a second communicating hole 53 which enables the reaction chamber 2 to communicate with the second buffer chamber 3, and a fourth gate valve 43 is provided to a third communicating hole 54 which enables the second buffer chamber 3 to communicate with the rinsing chamber 4. Either of the first and the second gate valve, 40 and 41, and either of the third and the fourth gate valve, 42 and 43, are kept closed always, so that the reaction chamber 2 is prevented from communicating with the open air.