A usage measuring device measures usage of a gear transmission. The usage measuring device is provided with an oscillation cycle measuring unit and a comparing unit. The oscillation cycle measuring unit measures an oscillation cycle of a state signal indicating at least one of a rotational state of an input unit side and a rotational state of an output unit side of the gear transmission. The comparing unit compares a first oscillation cycle measured during an initial operating period of the gear transmission, and a second oscillation cycle measured after the gear transmission has operated for a predetermined time. The oscillation cycle measuring unit measures the first oscillation cycle and the second oscillation cycle of the state signal after the gear transmission has stopped driving.