An angular rate sensor has a vibrator vibrating along a reference direction at a fixed frequency in response to a driving signal, and vibrating along a detecting direction perpendicular to the reference direction in accordance with an angular velocity given to the vibrator. A monitoring signal generator generates a monitoring signal having a waveform of the vibrator vibration along the reference direction. A clock signal generator generates, from the monitoring signal, a first clock signal and a second clock signal having a frequency identical with that of the first clock signal and a level change occurring at a time differing from that in the second clock signal. The first clock signal is used to maintain the vibrator vibration along the reference direction. An angular velocity detector detects the angular velocity from a waveform of the vibrator vibration along the detecting direction by using the second clock signal.