Intrusion of foreign matters from the outside of a reaction container plate and environmental contamination onto the outside are prevented. The reaction container plate (1) comprises a container base (3) having a reaction container (5), a channel base (11) having an introduction hole (11b) above the reaction container (5) and arranged on the surface of the container base (3), and a channel cover (13) arranged on the channel base (11) in order to form in cooperation with the surface of the channel base, an introduction channel (15) passing above the introduction hole (11b). The channel (13) is formed to be enclosed. The introduction hole (11b) does not allow liquid to pass under an introduction pressure state in the channel (15) where the liquid is introduced into the channel (15) but allows the liquid in the channel (15) to pass to the reaction container (5) side under a pressurized state where the inside of the channel (15) is pressurized higher than the introduction pressure. The channel cover (13) is composed of a flexible member, and, when it is urged to the channel base (11) side after the liquid is introduced into the channel (15), the inside of the channel (15) is brought into a pressurized state and the liquid is passed through the introduction hole (11b) and injected into the reaction container (5).