To solve the problem wherein an anxiety about a fall of battery voltage may cause such incovenience on measurement that when the voltage falls down to the voltage transition to a charge warning voltage, a chronograph thought to operate normally suddenly stops against intention of a user.

The voltage detection means detects: a 1st action state representing the voltage state in which the watch is capable of normal action; and a 2nd action state of the voltage lower than that the 1st action state and a charge warning voltage state for ensuring the minimum action of the watch, thereby the measurement action is maintained for one measurement until the measurement is finished, even when the voltage detection means detects that the voltage is transferred from the 1st action state to the 2nd action state while the time measurement means is making the measurement action.