A concrete vibrator can automatically change the rotational speed of a motor depending on the state of a vibrating tube. Under control by a controller, the concrete vibrator is operated in a normal mode in which the motor is supplied with driving power having a frequency to make the motor rotate at a rotational speed suitable for air bubble removal, or in an idling mode in which the motor is supplied with driving power having a frequency to make the motor rotate at a lower rotational speed than in the normal mode. The controller measures, per unit of time, a value of a current that is input to the controller or motor, compares a latest current value to a reference value calculated based on a past measurement value, and compares an absolute value of the comparison value to a threshold to grasp the state of the vibrating tube.