Not only a downsized cartridge but also an aperture constituted simply and at low cost using a downsized configuration of the cartridge is provided. A measurement channel includes a front-surface-side channel unit provided on a front surface of a cartridge main body; a rear-surface-side channel unit provided on a rear surface of the cartridge main body; and a connection channel unit connecting the front-surface-side channel unit to the rear-surface-side channel unit. An aperture is formed in the connection channel unit, a fluid contact unit of one electrode is arranged in the front-surface-side channel unit, and a fluid contact unit of the other electrode is arranged in the rear-surface-side channel unit.