A plate-shaped fuel cell separator comprising: a reaction gas supply manifold hole which is provided in a peripheral portion of the fuel cell separator to penetrate through the fuel cell separator in a thickness direction thereof; a reaction gas discharge manifold hole which is provided in a peripheral portion of the fuel cell separator to penetrate through the fuel cell separator in a thickness direction thereof; a groove-shaped first reaction gas channel which is formed in at least one of principal surfaces of the fuel cell separator such that an upstream end thereof is connected to the reaction gas supply manifold hole, a downstream end thereof is connected to the reaction gas discharge manifold hole, and the first reaction gas channel is bent; and one or more groove-shaped second reaction gas channels which are formed in at least one of the principal surfaces such that at least upstream ends thereof are connected to the reaction gas supply manifold hole and are bent while running along the first reaction gas channel; wherein the first reaction gas channel includes an upstream portion, a midstream portion formed in a spiral shape and a downstream portion, and the midstream portion is surrounded by the upstream portion and the downstream portion; wherein the upstream portion of the first reaction gas channel includes a second portion; wherein the downstream portion of the first reaction gas channel includes a first portion; wherein the first portion of the first reaction gas channel is a portion lying closest to the upstream end among portions located between the second portion and the downstream end of the first reaction gas channel, the second portion of the first reaction gas channel is a portion lying closest to the downstream end among portions located between the upstream end and the first portion of the first reaction gas channel, and the one or more second reaction gas channels do not exist between the first portion and the upstream end of the first reaction gas channel but exist between the second portion and the downstream end of the first reaction gas channel, characterized in that the first reaction gas channel is in fluid communication with a specific channel which is at least one of the one or more second reaction gas channels, in a specific portion existing between the first portion and the downstream end. a reaction gas supply manifold hole which is provided in a peripheral portion of the fuel cell separator to penetrate through the fuel cell separator in a thickness direction thereof; a reaction gas discharge manifold hole which is provided in a peripheral portion of the fuel cell separator to penetrate through the fuel cell separator in a thickness direction thereof; a groove-shaped first reaction gas channel which is formed in at least one of principal surfaces of the fuel cell separator such that an upstream end thereof is connected to the reaction gas supply manifold hole, a downstream end thereof is connected to the reaction gas discharge manifold hole, and the first reaction gas channel is bent; and one or more groove-shaped second reaction gas channels which are formed in at least one of the principal surfaces such that at least upstream ends thereof are connected to the reaction gas supply manifold hole and are bent while running along the first reaction gas channel; wherein the first reaction gas channel includes an upstream portion, a midstream portion formed in a spiral shape and a downstream portion, and the midstream portion is surrounded by the upstream portion and the downstream portion; wherein the upstream portion of the first reaction gas channel includes a second portion; wherein the downstream portion of the first reaction gas channel includes a first portion; wherein the first portion of the first reaction gas channel is a portion lying closest to the upstream end among portions located between the second portion and the downstream end of the first reaction gas channel, the second portion of the first reaction gas channel is a portion lying closest to the downstream end among portions located between the upstream end and the first portion of the first reaction gas channel, and the one or more second reaction gas channels do not exist between the first portion and the upstream end of the first reaction gas channel but exist between the second portion and the downstream end of the first reaction gas channel, characterized in that the first reaction gas channel is in fluid communication with a specific channel which is at least one of the one or more second reaction gas channels, in a specific portion existing between the first portion and the downstream end.