A method and a reaction apparatus which can safely and continuously treat/discharge especially a short object is treated without any direct contact with a gas atmosphere, and which surely/efficiently treats the object with a gas without any uneven treatment. A short object A to be treated is put in a hermetically sealed cylindrical treatment section 1. In the treatment section 1, the object is held in a predetermined position by a first operation piece 11 to be treated with a gas for a predetermined time. Then, the holding by the first operation piece is released to move the object A by a desired distance. Subsequently, the object is held in a predetermined position by a second operation piece 12 to be treated again with the gas for a predetermined time, and then a treated object A1 is discharged. This discharged treated object A1 is conveyed to the outside of the apparatus.