An environmental information
measurement device includes: a power source unit; an environmental information
detector; a
timer; and a controller. The power source unit generates, from an electromagnetic wave received, a power source
voltage to be supplied to a load. The load includes the environmental information
detector, the
timer, and the controller. The environmental information
detector includes a detector including a circuit element having an impedance or an electrostatic
capacitance that varies according to a physical amount detected under an environment at a measurement target point, and outputs a
signal that varies according to a response characteristic of the detector. The
timer measures a duration from the time when measurement is initiated to the time when a
voltage of the
signal becomes a predetermined detection
voltage. The controller controls an operation of the environmental information detector.