An electrochemical reaction cell stack comprising: an electrochemical reaction block (102G1) including three or more electrochemical reaction units arranged in a first direction, each of the electrochemical reaction units including an electrolyte layer , a cathode and an anode which face each other in the first direction with the electrolyte layer intervening therebetween, and an anode chamber facing the anode ; a first heat-absorbing member which is disposed on one side of the electrochemical reaction block (102G1) in the first direction and absorbs heat generated from the electrochemical reaction block (102G1); and a second heat-absorbing member which is disposed on the other side of the electrochemical reaction block (102G1) in the first direction and absorbs heat generated from the electrochemical reaction block (102G1), wherein: the three or more electrochemical reaction units include two or more upstream electrochemical reaction units , and one or more downstream electrochemical reaction units ; the electrochemical reaction cell stack includes a gas flow passage which communicates with the anode chamber included in each of the two or more upstream electrochemical reaction units and with the anode chamber included in each of the one or more downstream electrochemical reaction units , and which introduces a gas discharged from the upstream anode chamber into the downstream anode chamber ; and one or more of the upstream electrochemical reaction unit(s) is(are) disposed between the first heat-absorbing member and the downstream electrochemical reaction unit disposed closest to the first heat-absorbing member , the electrochemical reaction cell stack being characterized in that : one or more of the upstream electrochemical reaction unit(s) is(are) disposed between the second heat-absorbing member and the downstream electrochemical reaction unit disposed closest to the second heat-absorbing member. an electrochemical reaction block (102G1) including three or more electrochemical reaction units arranged in a first direction, each of the electrochemical reaction units including an electrolyte layer , a cathode and an anode which face each other in the first direction with the electrolyte layer intervening therebetween, and an anode chamber facing the anode ; a first heat-absorbing member which is disposed on one side of the electrochemical reaction block (102G1) in the first direction and absorbs heat generated from the electrochemical reaction block (102G1); and a second heat-absorbing member which is disposed on the other side of the electrochemical reaction block (102G1) in the first direction and absorbs heat generated from the electrochemical reaction block (102G1), wherein: the three or more electrochemical reaction units include two or more upstream electrochemical reaction units , and one or more downstream electrochemical reaction units ; the electrochemical reaction cell stack includes a gas flow passage which communicates with the anode chamber included in each of the two or more upstream electrochemical reaction units and with the anode chamber included in each of the one or more downstream electrochemical reaction units , and which introduces a gas discharged from the upstream anode chamber into the downstream anode chamber ; and one or more of the upstream electrochemical reaction unit(s) is(are) disposed between the first heat-absorbing member and the downstream electrochemical reaction unit disposed closest to the first heat-absorbing member , the electrochemical reaction cell stack being characterized in that : one or more of the upstream electrochemical reaction unit(s) is(are) disposed between the second heat-absorbing member and the downstream electrochemical reaction unit disposed closest to the second heat-absorbing member. <EOS>