Mechanical watch

A mechanical watch comprising:

• a spiral spring;
• a balance configured to be driven by power from the spiral spring;
• an oscillation circuit configured to output a clock signal;
• a vibration cycle detection unit configured to detect a vibration cycle of the balance and output a vibration cycle detection signal;
• a speed governing unit including a permanent magnet and a coil;
• a speed governing control unit configured to control the speed governing unit to perform a speed governing control of the balance;
• a storage unit configured to store an electrical energy to be supplied to the speed governing control unit;
• a generator configured to generate the electrical energy;
• and
• a power switch coupled between the coil and a power-source line configured to supply current to the coil, wherein
• one of the permanent magnet and the coil is held by the balance,
• the speed governing control unit compares the clock signal and the vibration cycle detection signal and performs the speed governing control of the balance by exerting an electromagnetic force on the permanent magnet, the electromagnetic force being generated by outputting current to the coil, and
• when a stored energy amount of the storage unit is equal to or smaller than a predetermined value, the speed governing control unit changes states to a stop state where the speed governing control of the balance is stopped, and
• the speed governing control unit changes the states to the stop state by turning the power switch off.