A microorganism number-measuring apparatus includes a container holder holding container (6) that accommodates a liquid into which microorganisms are released, power supply unit (27) applying a microorganism-collecting voltage and a microorganism number-measuring voltage to measurement electrode (3) that is dipped in container (6) held by the container holder, and reuse prevention unit (32) that makes measurement electrode (3) burn out after a measurement operation thereof. With this configuration, it is possible to prevent improper reuse of the measurement electrode.
