The number and combination of N-pole connectors (41) and (N + 1)-pole connectors (42) are decided so that the number of cells (19) of a fuel cell stack (23) is equal to the number of terminal side connectors (40). Accordingly, the terminal side connectors (40) do not have any reserved pole. For this, as compared to a case when the terminal side connectors (40) have a reserved number of poles, it is possible to eliminate wastes and reduce the size of a multi-channel measuring device (10), which brings about an advantage in a space. Moreover, even when the number of cells (19) of the fuel stack(23) is modified, there is no need of arranging a new terminal connector (40) other than the N-pole and (N + 1)-pole connectors. What is required is only to change the number and the combination of the N-pole connectors (41) and the (N + 1)-pole connectors (42). Accordingly, it is possible to easily cope with modification of the number of cells (19) of the fuel cell stack (23).