A measuring apparatus includes: a measuring circuit configured to carry out predetermined processing for the measurement result of an object to be measured; a communication control circuit configured to generate output data to be output externally depending on the processing result of the measuring circuit; a power source circuit having a charging element configured to supply power to the measuring circuit and the communication control circuit; an output circuit having open-drain output terminals configured to externally output the output data generated in the communication control circuit; and a charge control circuit configured to charge the charging element at the timing when the output data is not output externally, the open-drain output terminals of the output circuit being used as the input terminals thereof.