A pulse wave measuring device includes: a connector that is disposed on a main unit an external sensor that includes an external light-emitting module radiating light to a human body to be measured and an external light-receiving module receiving at least one of reflected light and transmitted light originating from the external light-emitting module and the human body so as to measure a pulse wave an first controller that switches the external light-emitting module ON and OFF an second controller that switches the external light-receiving module ON and OFF and an external sensor connection determination section that determines a connection between the external sensor and the connector in accordance with a transient response of the external light-receiving module, wherein, after the external sensor connection determination section determines that the external sensor is connected to the connector, a measurement of the pulse wave by using the external sensor is started.
