A mechanical timepiece has a mainspring for generating a rotational force and a front train wheel for undergoing rotation in accordance with a rotational force generated by the mainspring. An escapement/speed-control device for controlling rotation of the front train wheel has a balance with hairspring for undergoing reciprocal rotational movement, an escape wheel and pinion for undergoing rotation in accordance with rotation of the front train wheel, and a pallet fork for controlling rotation of the escape wheel and pinion in accordance with rotation of the balance with hairspring. A switch mechanism outputs an ON signal when a rotation angle of the balance with hairspring becomes a predetermined threshold angle or greater and outputs an OFF signal when the rotation angle of the balance with hairspring does not exceed the predetermined threshold angle. A position-detecting device detects a position of the mechanical timepiece. A balance-with-hairspring rotation angle control mechanism applies a force to suppress rotation of the balance with hairspring when the switch mechanism outputs an ON signal in accordance with a position of the mechanical timepiece detected by the position-detecting device.