ELECTROCHEMICAL REACTION CELL STACK

To prevent impairment of the sealing performance of a fuel gas flow channel, which would otherwise occur due to reduction reaction between a first coating and a fuel gas. An interconnector-electrochemical reaction unit cell composite body includes an electrochemical reaction unit cell, and an interconnector which has a first through hole defining a fuel gas flow channel and which is disposed on the side toward an anode of the electrochemical reaction unit cell. The interconnector includes a coating forming a first surface of the interconnector opposite the anode of the electrochemical reaction unit. The coating includes a first coating and a second coating having reduction resistance higher than that of the first coating. The first coating forms a first surface region which is a portion of the first surface of the interconnector and which is located away from the first through hole. The second coating forms a second surface region which is a portion of the first surface of the interconnector, which surrounds the first through hole, and which is located between the first coating and the first through hole.