Provided is a radio-controlled wristwatch that receives a radio wave including day-related information from a satellite within a global positioning system, in which a cycle number of the day-related information is correctly updated even in a case where a power supply voltage drops. A radio-wave wristwatch (1) according to the present invention includes: reception means (11) for receiving a radio wave from a satellite and extracting day-related information therefrom; timekeeping-circuit halting means for halting an operation of a timekeeping circuit based on a power supply voltage; timekeeping-circuit halt detection means for detecting that the operation of the timekeeping circuit (13) has been halted by the timekeeping-circuit halting means; a nonvolatile memory (23) for storing the day-related information and a cycle number of the day-related information; and cycle-number updating means for updating, when the timekeeping-circuit halt detection means detects that the operation of the timekeeping circuit has been halted, the cycle number of the day-related information based on a comparison result between the day-related information extracted by the reception means (11) and the day-related information stored in the nonvolatile memory (23).