Provided is a device and a method whereby plural kinds of reaction operations and washing operations can be conducted in parallel without washing or replacing an instrument used in transferring a solution in each operation. A reaction device having a plurality of projecting barriers provided in a line on one surface of a substrate. The projecting barrier has a cutoff portion and an inner space capable of holding a droplet and having a contact angle to pure water of from 90 to 150 degrees. A reaction method using the reaction device wherein a substance immobilized on magnetic beads is sequentially transferred in and between droplets of a solution containing a surface tension reducing agent that are held in the spaces for holding a droplet by means of a magnet located on the opposite surface of the substrate to thereby conduct reactions and washings.