To improve the visibility of a display element in a radiowave intensity measuring device for weak long-distance radiowaves.

A battery as a power supply for supplying electric power to the radiowave intensity measuring device is included and charged with the radiowaves received. The electric power is stored in the battery, when the potential of the signal obtained by the received radiowaves is larger than the output potential of the battery. The electric power of the battery generated is used as the power supply, to drive the radiowave intensity measuring device, when the potential of the signal obtained by the received radiowaves is smaller than the output potential of the battery. A thermochromic element or electrochromic element is used as an element for displaying the intensity of radiowaves.